Tamino XML Server Version 9.7
 —  X-Machine Programming  —

Requests using X-Machine Commands

This section describes how to communicate with the X-Machine using the X-Machine's own processing commands. It also describes the corresponding HTTP request and response structure.

The X-Machine offers a set of commands for storing, retrieving and deleting X-Machine documents, creating or erasing collections or schemas, performing transaction processing and diagnostic testing. These commands are sent to the X-Machine either as parameters that are appended to a URL in an HTTP GET request (parameterized URL addressing), or as HTML form data in an HTTP POST request.

The commands are:

Command Meaning
_admin Perform an administration function
_commit Commit a transaction
_connect Start a database session
_cursor Perform a cursor-related command
_define Create a collection, schema or doctype; modify an existing schema or doctype
_delete Delete one or more documents
_destroy

Remove a prepared query

_diagnose Perform a diagnostic test
_disconnect Terminate a database session
_execute

Execute a prepared query

_htmlreq Create and query Tamino documents (used only in the context of HTML forms)
_prepare

Prepare (precompile) a query for later execution

_process Store one or more documents into a collection; or modify an existing XML document
_rollback Roll back a transaction
_undefine Delete a collection, schema or doctype
_xql Retrieve one or more documents using the Software AG's XPath-based X-Query query language
_xquery Specify a query based on the W3C XQuery query language

X-Machine commands are described under the following headings:


X-Machine Command Format

Each X-Machine command described in this section can be sent either via an HTTP GET request or via a multipart form HTTP POST request.

X-Machine commands that are sent via HTTP GET requests are contained as keyword/value pairs in URLs according to the syntax given below (parameterized URL addressing). For some commands, additional information can be supplied in the form of keyword/value pairs.

For HTTP POST requests with HTML form data, only the URL prefix (the part specifying the path of the database to be accessed) is supplied as the HTTP address, and the keyword/value pairs are supplied in the body of the HTML form data.

In general, the examples in the following sections for the individual commands use parameterized URL addressing.

Parameterized URL addressing via HTTP GET

The syntax of parameterized URL addressing is as follows:

URLprefix/CollectionName{?Command[/Stylesheet]=Data[&Keyword=Value]}...

The syntax has the following meaning:

URLprefix

The URL of the database to be accessed, for example:

http://myhost:80/tamino/mydatabase

The host name and port number must point to the computer and port where your web server is running.

CollectionName

The name of the collection to be accessed. This is optional for some commands.

Command

The X-Machine command, which is one of the following verbs: _define, _undefine, _process, _delete, _xql, _xquery, _connect, _commit, _rollback, _disconnect, _admin, _cursor, _htmlreq or the special verb _diagnose, _destroy, _prepare, _execute.

Command names are case-insensitive.

Stylesheet

A URL pointing to an XSL stylesheet. When this is specified, the response to the request will contain an XSL processing instruction of the form:

<?xsl:stylesheet href='Stylesheet'?>

Browsers capable of interpreting such processing instructions (such as Internet Explorer) will format the response document according to the formatting specified in the stylesheet. Refer also to the section Syntax of XML Responses for information about the content of the response document.

The stylesheet may be specified either as an absolute URL starting with http:// or as a relative URL which is evaluated by the client application (web browser) according to the standard rules.

Example: If "_xql/http://aaa/bbb.xslt=patient" is specified, a processing instruction

<? xsl:stylesheet href='http://aaa/bbb.xslt' ?>

will be added to the response document.

Data

This specifies the data to be processed by the command. This can be XML documents or query expressions depending on the preceding verb, or parameters for commands such as _diagnose and _admin.

The transaction and session-related command verbs _connect, _commit, _rollback and _disconnect require an asterisk ("*") here, for example _commit=*, and the remaining data must be supplied in the form of keyword/value pairs (see the description of Keyword and Value below).

Keyword

The name of a keyword that further qualifies the processing to be done by the command.

There can be multiple keyword/value pairs. Each keyword/value pair must be preceded by an ampersand ("&").

Keywords are case-insensitive. Unknown keywords are ignored.

Value Value of the keyword. See the description of the commands below for information on the values allowed.

If the web server-based security mechanism is implemented at your site, the collection must be entered to the left of the question mark.

Restrictions when using parameterized URL addressing

If you use parameterized URL addressing rather than HTML form data, please be aware of the following restrictions:

HTML multipart form data via HTTP POST

For X-Machine commands sent in HTTP POST requests with HTML form data, the information sent is equivalent to that sent by parameterized URL addressing (see the section Parameterized URL addressing via HTTP GET above), but the keyword/value pairs are supplied in the body of the HTML form data.

Here is an example of the HTTP request body using the _define command to define a schema cluster consisting of 2 schemas S1 and S2:

POST /tamino/myDB HTTP/1.1
User-Agent: ….
Content-Type: multipart/form-data; boundary=xYzZY
Content-Length: 1250
Host: localhost:80
Accept: text/html, image/gif, image/jpeg, *; q=.2, */*; q=.2
Connection: keep-alive

--xYzZY
Content-Disposition: form-data; name="_define"
Content-Type: text/plain
Content-Length: 7

$S1,$S2
--xYzZY
Content-Disposition: form-data; name="$S1"

<?xml version="1.0" encoding="utf-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" 
     xmlns:tsd="http://namespaces.softwareag.com/tamino/TaminoSchemaDefinition">
   <xs:annotation>
      <xs:appinfo>
         <tsd:schemaInfo name="S1">
            <tsd:collection name="cluster"/>
            <tsd:doctype name="root"/>
         </tsd:schemaInfo>
      </xs:appinfo>
   </xs:annotation>

   <xs:element name="root">
     <xs:complexType>
       <xs:sequence>
         <xs:element ref="child"/>
       </xs:sequence>
     </xs:complexType>
   </xs:element>

   <xs:element name="child"/>

</xs:schema>

--xYzZY
Content-Disposition: form-data; name="$S2"

<?xml version="1.0" encoding="utf-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" 
     xmlns:tsd="http://namespaces.softwareag.com/tamino/TaminoSchemaDefinition">
   <xs:annotation>
      <xs:appinfo>
         <tsd:schemaInfo name="S2">
            <tsd:collection name="cluster"/>
         </tsd:schemaInfo>
      </xs:appinfo>
   </xs:annotation>

</xs:schema>

--xYzZY--

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Description of X-Machine Commands

This section describes the individual X-Machine commands. The list of available commands is as follows:

Warning:
Web servers that log requests log the URL but not the body of the request. So if a user issues a request using a GET, the data can be obtained by reading the web server log, which could lead to potential security or privacy problems. If PUT or POST are used, the data cannot be seen in the web server log.

The _admin command

The _admin command offers several administration functions for Tamino. The format of this command is:

_admin=Function(Parameter, ...)

After execution of the _admin command, the response document indicates either a successful execution or an error. In the case of success, a response such as the following will be delivered:

<ino:message ino:returnvalue="0">
<ino:messageline>
  starting admin command AdminCommand 
</ino:messageline>
</ino:message>
<ino:message ino:returnvalue="0">
<ino:messageline>
  admin command AdminCommand completed
</ino:messageline>
</ino:message>

Otherwise, in the case of an error, the response will contain entries like this:

<ino:message ino:returnvalue="Value">
<ino:messagetext ino:code="ErrorCode">
   MessageText
</ino:messagetext>
</ino:message>

The following administration functions are available.

The ino:Accessor function

This administration function allows a client to cancel a request that it submitted previously. This could be used, for example, to cancel a request that is taking a long time to execute.

In order to label a request so that it can be uniquely identified for cancellation at a later stage, the client assigns a unique request ID to the request when the request is sent to the X-Machine. This ID can be used in a later call of ino:Accessor("cancelRequest", "requestID") to cancel the execution of the request. The request ID consists of a unique part generated by the X-Machine, obtained by a call of ino:Accessor("getId"), plus a client-generated part.

The function can be called with the following parameters:

ino:Accessor("getId")

When this command is sent to the X-Machine, the X-Machine returns a server-generated unique ID in the HTTP response header field X-INO-clientRequestId. In any subsequent request from the client to the X-Machine, the client can pass a request ID, constructed from the server-generated unique ID, in the HTTP request header field X-INO-clientRequestId to label the request uniquely, so that the request can be cancelled by a subsequent call of ino:Accessor("cancelRequest", "requestID").

The request ID is composed of the server-generated unique ID plus a client-generated part. The client generated part can be freely chosen, as long as the resulting request ID for a given request is unique.

The request ID must be UTF-8 encoded.

ino:Accessor("cancelRequest", "requestID") This command cancels the request identified by the requestID. The meaning of requestID is described above.

A typical flow of events is shown in the following diagram. In this example, the initial call of _admin=ino:Accessor("getId") returns the server-generated unique ID "SGUID" in the HTTP header field X-INO-clientRequestId in the response. The request ID generated by the client for each subsequent request has the format "SGUID-nn", where nn is a numeric counter starting from "01". The example shows two requests, with the request IDs "SGUID-01" and "SGUID-02", with each request sending an _XQUERY command. To cancel the request that has the request ID "SGUID-02", the client issues the command ino:Accessor("cancelRequest", "SGUID-02").

graphics/cancel.png

Related information

The ino:Accessor function is used by a client to cancel a request that it previously submitted itself. A user with administration rights can also cancel any active Tamino request, regardless of which client originally submitted it, by using the ino:Request function of the _admin command.

The ino:CancelMassLoad function

This administration function allows you to cancel a halted session of the Tamino data loader utility on the Tamino server machine. This situation can arise if the client machine from which the mass load was started has become unavailable. The call has one parameter, namely a string specifying either (a) the desired doctype and the respective collection or (b) the session ID:

_admin=ino:CancelMassLoad("CollectionName/DoctypeName" | SessionID)

Note:
This function can only cancel a session that is inactive, i.e., you cannot stop a running session.

If the function completes successfully, the reply of this function will contain entries like these:

<ino:message ino:returnvalue="0">
   <ino:messageline>session 12345 ended</ino:messageline>
</ino:message>

If no active session was found you will receive a result document containing entries like these:

<ino:message ino:returnvalue="8555">
   <ino:messageline>Invalid session ID</ino:messageline>
</ino:message>

In the case of an active session but unsuccessful execution, the result document will contain entries like these:

<ino:message ino:returnvalue="8285">
   <ino:messageline>Invalid session ID</ino:messageline>
</ino:message>

If the function is issued against a doctype for which no data loader session is halted, an error response 8310, "Invalid parameter detected" will be returned.

The ino:ChangeUserPassword function

This function allows a user to change his or her password.

The function has one parameter, which is the new password in plain text:

_admin=ino:ChangeUserPassword("NewPassword")

For further information about this command, refer to the section Tamino Security in the documentation of the Tamino Manager.

The ino:DisplayIndex function

The function ino:DisplayIndex displays the contents of standard indices or text indices. The description of this function consists of the following sections:

Syntax

The function call has the following syntax:

_admin=ino:DisplayIndex("CollectionName", "ElementPath", "StartValue", "Size", "IndexType")

where CollectionName is the name of the collection, ElementPath is the absolute path of the indexed element, StartValue is the first index value that you want to display, Size is the number of values to display for the index (must be a positive integer), and IndexType specifies the index type, which can be one of "standard", "text", "multipath-standard", "multipath-text" or "computed-standard".

Example
_admin=ino:DisplayIndex("Customers","Customer/Name","B","10","standard")

This will display the first 10 values that exist for the standard-indexed element Name in the doctype Customer in the collection Customers. The start value "B" indicates that the first value returned for the index should be equal to or greater than "B". The result document could, for example, contain the following lines:

<ino:index ino:indexcoll="Customers" ino:indexpath="Customer/Name" ino:indextype="standard">
  <ino:indexvalue ino:indexcount="28">Baker</ino:indexvalue>
  <ino:indexvalue ino:indexcount="33">Barclay</ino:indexvalue>
  <ino:indexvalue ino:indexcount="14">Bayliss</ino:indexvalue>
  <ino:indexvalue ino:indexcount="1">Bean</ino:indexvalue>
  <ino:indexvalue ino:indexcount="28">Bedford</ino:indexvalue>
  <ino:indexvalue ino:indexcount="23">Bingham</ino:indexvalue>
  <ino:indexvalue ino:indexcount="676">Black</ino:indexvalue>
  <ino:indexvalue ino:indexcount="22">Bolton</ino:indexvalue>
  <ino:indexvalue ino:indexcount="563">Brown</ino:indexvalue>
  <ino:indexvalue ino:indexcount="47">Butler</ino:indexvalue>
</ino:index>

The collating sequence used for the ino:DisplayIndex function is the standard sequence of Unicode scalar values ("codepoints").

If there are several indexes of the specified index type at the given path, then all indexes will be displayed, and each index will have its own ino:index element, as described below. If there are several indexes, the given size (number of values to display) will apply to each index. If there are several indexes, the given start value will apply to each index (see also below the special case for a compound index). The index type specifies whether standard or text indexes are to be displayed. There is no further possibility to select an index of a specific kind (e.g., display only multipath indexes), or to select a particular index (e.g., the third out of five compound indexes).

Indexes are not available while they are built/rebuilt during a _define command or a ino:RecreateIndex/ino:RecreateTextIndex administration command. In this case the corresponding ino:index element will have its attribute ino:status set to "not-available". As the index values are being built at that point in time, no ino:indexvalue elements will be displayed. For example:

<ino:index ino:indexcoll="myColl"
           ino:indexpath="myDoc/field"
           ino:indextype="standard"
           ino:status="not-available">
</ino:index>
Standard Index and Collation

If a non-composite standard index has a collation, then the index value will be displayed in hexadecimal format, as there is currently no possibility of converting it back to a readable value. The attribute ino:value of the ino:indexvalue elements will have the value "collation-encoded". For example:

<ino:index ino:indexcoll="myColl"
           ino:indexpath="myDoc/field"
           ino:indextype="standard">
  <ino:indexvalue ino:indexcount="1" ino:value="collation-encoded">value1
  </ino:indexvalue>
  <ino:indexvalue ino:indexcount="1" ino:value="collation-encoded">value2
  </ino:indexvalue>
</ino:index>
Standard Index With Truncated Values

Tamino sets an upper limit on the length of an index, and indexes that exceed this limit are truncated. Information about the size of this limit in the current Tamino release is provided in the section Definition of Unique Keys in the Tamino XML Schema User Guide.

If a standard index contains a truncated value, the corresponding ino:index element will have the attribute ino:status set to the value "has-truncated-values". The corresponding index values that are truncated will be marked similarly. For compound indexes this was already described above. For simple standard indexes the ino:indexvalue element will have the attribute ino:value set to "truncated". As far as possible the truncated value will appear as the contents of ino:indexvalue. For example:

<ino:index ino:indexcoll="myColl"
           ino:indexpath="myDoc/field"
           ino:indextype="standard"
           ino:status="has-truncated-values">
  <ino:indexvalue ino:indexcount="1" ino:value="truncated">value1
  </ino:indexvalue>
  <ino:indexvalue ino:indexcount="1">value2</ino:indexvalue>
</ino:index>

For more information on truncated values, refer to the section

Index options

Depending on the index type (standard or text), the options compound and multipath can be available. These options may be combined: a compound index (or more precisely, a standard index with the compound option) may be part of a multipath index. Moreover, several indexes of the same kind may occur at a particular path. For example, an element may have several compound indexes.

The compound and multipath options are represented as an attribute of the ino:index element. If an index has several options, then all the corresponding attributes will appear with the ino:index element.

Compound Index

A compound index is represented by an ino:fields attribute, the value of which is the concatenation of the index components as given in the schema (separated by blanks). The following example shows a schema with a compound index and the corresponding ino:index element in the index display:

Schema with a compound index
<xs:element ...>
  ...
  <tsd:elementInfo>
    <tsd:physical>
      <tsd:native>
        <tsd:index>
          <tsd:standard>
     		     <tsd:field xpath="C"/>
     		     <tsd:field xpath="B/@b" />
          </tsd:standard >
	         ...
        </tsd:index>
      </tsd:native>
    </tsd:physical>
  </tsd:elementInfo>
<xs:element>
ino:index element in the index display
<ino:index ino:indexcoll="myCollection"
           ino:indexpath="myDocument/myElement"
           ino:indextype="standard"
           ino:fields="C B/@b">

The following general rules apply for the display of compound indexes:

Unique Keys

There is no explicit way to display unique keys. As they are implemented as standard/compound indexes, they are displayed implicitly when ino:DisplayIndex() is called with a path at which such an index exists. Consider for example the following schema:

Schema with unique key
<tsd:doctype name="A">
 	...
	 <tsd:unique name="CB-key">
	  	<tsd:field xpath="C"/>
		  <tsd:field xpath="B/@b" />
	   </tsd:unique>
	 <tsd:unique name="D-key">
		  <tsd:field xpath="D"/>
	 </tsd:unique>
	 ...
</tsd:doctype>

This example means that if ino:DisplayIndex() is called with "path="A/D"", then the unique key "D-key" will be displayed, and if ino:DisplayIndex() is called with "path="A"", then the unique key "CB-key" will be displayed. In both cases, the attribute ino:unique="true" in the ino:index element will identify the indexes as unique keys:

<ino:index ino:indexcoll="myCollection"
           ino:indexpath="A/D"
           ino:indextype="standard"
           ino:unique="true">

<ino:index ino:indexcoll="myCollection"
           ino:indexpath="A "
           ino:indextype="standard"
           ino:fields="C B/@b"
           ino:unique="true">
Multipath Index

For a multipath index, the label as given in tsd:multiPath will be displayed in the ino:multiPath attribute. Consider the following sample schema:

<xs:element name = "Title" type = "xs:string">
  <xs:annotation>
    <xs:appinfo>
      <tsd:elementInfo>
        <tsd:physical>
          <tsd:native
            <tsd:index>
              <tsd:text>
                <tsd:multiPath>MultiPathIndex</tsd:multiPath>
              </tsd:text>
            </tsd:index>
          </tsd:native>
        </tsd:physical>
      </tsd:elementInfo>
    </xs:appinfo>
  </xs:annotation>
</xs:element>

The ino:index element shown for this schema is:

<ino:index ino:indexcoll="myCollection"
           ino:indexpath="myDocument/Title"
           ino:indextype="text"
           ino:multiPath="MultiPathIndex">

As a multipath index in general is not based on a specific path in the doctype, it is also possible to display the entries of a specific multipath index by using the following extended syntax:

_admin=ino:DisplayIndex("Collection", "Doctype/IndexName", "StartValue", "Size", "IndexType")

where IndexName is the name specified in the tsd:multipath element, and IndexType is either "multiPath-standard" or "multiPath-text".

Computed Index

For an example schema defining a computed index see e.g. Appendix 5: Example Schemas for Indexing in the XML Schema User Guide. It is possible to display the entries of a computed index by using the following extended syntax:

_admin=ino:DisplayIndex("Collection", "Doctype/IndexName", "StartValue", "Size", "IndexType")

where IndexName is the value of the name attribute of the tsd:computed element, and IndexType must be "computed-standard".

Reference Index

For a reference index, the label as given in tsd:refers will be displayed in the ino:refers attribute. Consider the following sample schema:

<xs:element name = "D" minOccurs = "0" type="xs:string">
  <xs:annotation>
    <xs:appinfo>
      <tsd:elementInfo>
        <tsd:physical>
          <tsd:native>
            <tsd:index>
              <tsd:standard>
                <tsd:refers>/A/B</tsd:refers>
              </tsd:standard>
            </tsd:index>
          </tsd:native>
        </tsd:physical>
      </tsd:elementInfo>
    </xs:appinfo>
  </xs:annotation>
</xs:element>

The ino:index element shown for this schema is:

<ino:index ino:indexcoll="myCollection"
           ino:indexpath="A/B/D"
           ino:indextype="standard"
           ino:refer="/A/B">

The ino:Index function

This function is intended for performing maintenance tasks on indexes. The syntax is

_admin=ino:Index("Action"[,"CollectionName"[,"DoctypeName"]])

The parameter Action determines the action to be performed for the given doctype within the given collection. If the doctype name is omitted, all doctypes will be processed. If the collection name is omitted, all doctypes in all collections will be processed.

Currently, the only value supported for Action is "optimize". It causes the following steps to be executed for each doctype being processed:

  1. Optimize the internal storage used for the maintenance of long index values. This refers to index entries whose length exceeds 1000 bytes. Note that the length of an index entry depends strongly on the underlying datatype. For strings, the length of the UTF-8 representation is relevant.

    The ino:DisplayIndex function can be used to check whether such long index values have occurred. The result may look as follows:

    <ino:index ino:indexcoll="myCollection"					
               ino:indexpath="myDocument/myElement"				
               ino:indextype="standard"						
               ino:status="has-truncated-values">				
    

    The function ino:Index("optimize",...) should be used when a considerable amount of data has been deleted. This may speed up query execution considerably.

  2. Shrink the size of the structure index if possible. The structure index may contain paths which have been added when storing documents which have been deleted in the meantime. Again, using the function ino:Index("optimize",...) may improve the performance of query execution.

The ino:RecreateIndex function

The function ino:RecreateIndex causes the regeneration of all index information related to a given doctype. This includes all types of indexes:

The intended use of this function is to rebuild the indexes of a doctype in cases where indexes have been corrupted. If you wish to recreate the text indexes only, use the command ino:RecreateTextIndex instead.

Warning:
During normal operation, indexes are kept consistent by Tamino, and there is no reason to use this function. If, however, you think that a certain index should be recreated, the recommended method is to use the Tamino Schema Editor as described in the section Maintaining Tamino Indexes.

Function call

The function call has two parameters, namely the desired doctype and the collection it resides in. The syntax is:

_admin=ino:RecreateIndex("CollectionName", "DoctypeName")

The ino:RecreateTextIndex function

The function ino:RecreateTextIndex causes the regeneration of all text indexes for a given doctype within the database. A example of the usage of this function is to recreate text indices after the language tokenizer has been changed. Its call has two parameters, namely the desired doctype and the collection it resides in. The syntax is:

_admin=ino:RecreateTextIndex("CollectionName", "DoctypeName")
Warning:
Do not change the setting of the language tokenizer while this function is in progress.

If you change the language tokenizer (for example, from "white space-separated" to "japanese", on platforms where this is supported), you must run the function ino:RecreateTextIndex to re-create the text indices, unless the doctype was empty.

The ino:RepairIndex function

The function ino:RepairIndex is used to fix indexes that are incomplete. It is called with 3 parameters:

_admin=ino:RepairIndex("CollectionName", "DoctypeName", "action")

The use of this function is necessary under various conditions such as:

In all cases, none of the affected indexes can be used for query optimization, which may result in decreased performance of query execution and a higher server load.

There are two conceptually different ways to fix the problem, as indicated by the parameter action, which can take one of the following values:

During server startup, Tamino checks whether one or more incomplete indices exist, and writes appropriate messages to the job log. Therefore, after an unexpected interruption of operation such as a power failure, check the job log for such messages. If necessary, issue ino:RepairIndex for the reported doctypes to prevent performance degradation.

The job log could, in such a case, contain messages such as the following:

Info: (INOAAI0574) Starting database 'mydb'
Info: (INODSA1002) Tamino server 4.2.1 on Windows ...
Info: (INOXHI8265) Default tokenizer 'white space-separated'
Info: (INOXRI8801) Request to create indexes for doctype Play
                   in collection Shakespeare is pending
Info: (INODSI1452) Server session 3 started
Info: (INODSI1636) Tamino server successfully started

The ino:Request function

The function ino:Request allows the administrator to cancel any currently active Tamino client request, regardless of which client originally issued the request. It is called with 2 parameters:

_admin=ino:Request("cancel", "requestID")

The request ID is a unique identifier by which the X-Machine identifies currently active requests.

To determine the IDs of all active requests, issue the following XQuery command:

declare namespace tf='http://namespaces.softwareag.com/tamino/TaminoFunction'
tf:current-requests()

In the xq:result section of the response document of this XQuery command, details for each active Tamino request are provided in an ino:request element. The required request ID is given by the value of the attribute id. Here is a sample ino:request element, in which the request ID has the value "00000002":

<ino:request bytes_returned="0" collection="ino:collection" duration="0"
    http_method="POST" id="00000002" memory_usage="1535992"
    started="2008-08-06T07:03:16+02:00" status="active">
  <ino:from
    remote_address="nnn.nnn.nnn.nnn" server_host="MyHost"
    server_software="Apache/2.2.9 (Win32)"
    user_agent="Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.16) Gecko/20080702 Firefox/2.0.0.16"/>
  <ino:command value="declare namespace tf='http://namespaces.softwareag" verb="_XQUERY"/>
</ino:request>

If the client that originally issued the request assigned a request ID (see the description of the ino:Accessor administration function for details), the value of the id attribute will be the value of the client-assigned request ID, otherwise the value of the id attribute will be a system-generated value.

You can prevent unauthorized usage of the administration function ino:Request and the XQuery command tf:current-requests() by defining appropriate access control elements (ACEs) using the Tamino Security Manager, as well as the required access control lists (ACLs) and user groups. See the description of ACEs, ACLs and user groups in the Security Manager section of the Tamino Manager documentation for details. Note that when you add an ACE, the Security Manager dialog asks you to specify a node name for which the ACE applies. Instead of entering a node name in the ACE dialog, enter the function name ino:Request() or tf:current-requests(). If you specify tf:current-requests(), a further dialog will ask you to define the namespace tf; in this case, use the namespace declaration shown above.

Related information

The ino:Request function is used by the administrator to cancel any active Tamino request, regardless of which client originally submitted it. Clients without administrator rights can cancel their own requests using the ino:Accessor function of the _admin command.

The _commit command

The _commit command is used to commit the database changes made so far during the current transaction. A new transaction is started automatically when the next command in a session is received that causes an update or acquires a lock.

Note:
For a summary of restrictions, see the section Transaction-Related Commands.

Example:

URLprefix?_commit=*&_sessionid=479356&_sessionkey=220815

The _connect command

The _connect command is used to establish a session. A session ID and a session key are returned in the X-Machine response. The first subsequent command to the X-Machine must specify this session ID and session key using the _sessionid and _sessionkey parameters. The session ID must be supplied unchanged in all subsequent commands for the current session. The session key is a unique identifier for the current command. Each time the X-Machine receives a command that contains the session ID and session key from the previous response, it processes the current command and returns a new session key to be used in the next command. The X-Machine uses an algorithm to generate each new session key; it does not simply increment the old session key.

The first transaction in the session is started implicitly as soon as the X-Machine receives a command that changes the database, such as the _process command, or as soon as a command is issued that acquires a lock.

The command can take the parameter _QueueNextRequest with the value of "yes" or "no". This parameter specifies whether or not it is possible to send a new request in the session before the response of the previous request in the session has been fully received. The value you specify for this parameter overrides the value of the server XML parameter queue next request for the duration of the session. See the section Queuing a Follow-Up Request for further information.

Example:

To establish a session, specify the following.

URLprefix?_connect=*

When you start a session, you can specify the access rights that other users or applications can have to the data that is processed during the session. See the section Session Parameters for details.

The _cursor command

The cursor command is used for processing the result of a query that uses XQuery (via the _xquery command) or X-Query (via the _xql command). The result is a sequence of items for XQuery or a node set for X-Query. The cursor allows you to position within that sequence. The items of the sequence are arbitrary nodes and values.

Any number of cursors may be defined and used within the same session. To identify any given cursor, a handle is used. This is an identifier that is returned by Tamino in the response document of the initial "_cursor=open" request that defines the cursor. Subsequent requests that involve the cursor must specify the option "_handle=Handle".

A cursor is opened using the option "_cursor=open". In subsequent requests using the option "_cursor=fetch", a number of entries starting at a given position in the result set can be retrieved by specifying "_position=Position" and "_quantity=Quantity". The subset of the result set fetched when "_position" and "_quantity" are specified is termed the fetch set.

If the option "_scroll=yes" is specified when the cursor is opened, the value specified for Position in subsequent fetches for the same cursor can be anywhere in the range from 1 to the maximum number of entries in the result set.

If the option "_scroll=no" is specified when the cursor is opened, the value specified for Position in subsequent fetches for the same cursor must be higher than the last entry returned from the previous fetch. Thus, if a fetch returns the entries 101-110, the lowest entry that can be returned from the next fetch is 111. In this example, a subsequent fetch could return entries 111-115 or 125-140, but not 105-115.

The default value for scroll is "_scroll=no".

The parameter _sensitive is required when opening a cursor with _xquery. Legal values are "no" and "vague". If you specify "_sensitive=no", an insensitive cursor is opened. This means that the query is calculated on a fixed input when the cursor is opened, and thus the result sequence remains unchanged as long as the cursor is active. If you specify "_sensitive=vague", a vague cursor is opened. The query is calculated on an input that takes modification operations of parallel transactions into account. Thus, the result sequence can vary during the lifetime of the cursor if documents that match the original query criteria are inserted, updated or deleted in the meantime.

Note:
A transaction that has an open vague cursor cannot perform document modifications (update, insert, delete). A transaction that has an open insensitive cursor can do XQuery updates.

With cursors in the context of an _xql command, the behaviour always implicitly corresponds to "_sensitive=vague". You can specify the _sensitive parameter explicitly, but the only valid value is "vague".

The parameter _count allows you to specify whether the response document should contain a count of the number of documents that satisfy the query. If you specify "_count=no", no count is returned. If you specify "_count=cheap", the count is returned if Tamino can calculate this without major additional effort. The default value is "_count=no". If you specify any other value for the _count parameter, the default value is assumed. If a count is returned, it is delivered as the value of the attribute ino:count of the element ino:cursor. Tamino delivers no ino:count attribute if "_count=no" was specified or if Tamino cannot deliver the count without major additional effort.

Opening a cursor

To open a cursor, use a command of the following form. The commands are shown split across several lines for typographical reasons.

_cursor=open&_xquery=Query
[&_scroll={yes|no}]
&_sensitive={no|vague}
[&_count={no|cheap}]

or

_cursor=open&_xql=Query
[&_scroll={yes|no}]
[&_count={no|cheap}]

This identifies a set of entries that match the given query. All subsequent operations using this cursor will operate on this result set.

Get result documents

To retrieve entries from the result set, use a command of the following form:

_cursor=fetch&_handle=Handle&_position=Position[&_quantity=Quantity]

Here, Handle is the handle returned from the "_cursor=open" request, Position is the required starting position within the result set and Quantity is the number of entries to be returned. If you do not specify a quantity, the default value is 10.

Specifying "_quantity=0" is supported. It can be used for checking if a particular position, as given by the _position keyword, exists within the cursor. If a response document contains no error, the position exists in the cursor, otherwise the position does not exist in the cursor.

The position of the first cursor result is 1.

The result document contains

<ino:cursor ino:handle="Handle">
  <ino:current ino:position="p" ino:quantity="q"/>
  <ino:next ino:position="p+q"/>
  <ino:prev ino:position="p-q"/>
</ino:cursor>

where:

Handle is the handle of the cursor (generated by Tamino and returned in the result of the open cursor call).

p is the position as specified in the original request,

q is the quantity delivered (which usually is the quantity requested except at the end of the cursor),

The attribute ino:position in the elements ino:next and ino:prev gives the cursor position that would be required for a subsequent fetch request that uses the same cursor.

The element ino:prev is not returned in the case of a non-scrollable cursor, or if p is 1. If p-q is less than 1, ino:position will be set to 1. The element ino:next is not returned if there are no further results for the cursor.

Combining open and fetch

The open and fetch operations can be combined by using a request of the following form:

_cursor=open&_xquery=Query[&_scroll={yes|no}]&_sensitive={no|vague}
&_position=Position[&_quantity=Quantity]
or
_cursor=open&_xql=Query[&_scroll={yes|no}]
&_position=Position[&_quantity=Quantity]

Note:
If you are not working within the context of a Tamino session, this combination of open and fetch is the only cursor command that makes sense. You can fetch a subset of the query result set with this kind of command outside a Tamino session, but subsequent calls to fetch data from the cursor are not possible. Note that in XQuery this functionality should not be used as it is offered in a more efficient way as part of the query language by applying a position filter as the outermost expression ( (queryexpression)[position() ge start and position() le start + quantity] )

Close a cursor

To close a cursor, specify a command of the following form:

_cursor=close&_handle=Handle

Further aspects

In a session context, a cursor is implicitly closed at the end of a transaction.

If a cursor is opened outside the context of a session, it is closed immediately after the completion of the command in which it was opened.

Associated error messages

The error numbers are 8305 for an invalid handle, 8306 for an invalid position value, 8307 when trying to position backwards on a non-scrollable cursor.

If the query result when opening a cursor is empty, the cursor will still be created. Any attempt to fetch result documents from such a cursor will result in response 8306.

When trying to close a non-existing cursor, response 8305 will be returned.

Example

The following example illustrates how the cursor command is used.

  1. Open a session.

    URLprefix?_connect=* 

    Following this command, session SessionID with session key SessionKey is established.

  2. To open the cursor, use a command of the following form:

    URLprefix/Collection?_cursor=open&_sessionid=SessionID
    &_sessionkey=SessionKey&_xquery=Query

    Note that SessionID and SessionKey have to be specified without quotes. The Query represents your query statement. A handle is returned for the cursor (in this example the handle is assumed to have the value "1", as used in the following step). A new session key NewSessionKey is returned.

  3. Use the cursor to retrieve items from the result sequence. The new session key is required also.

    URLprefix/Collection?_cursor=fetch&_handle=1&_position=2
    &_quantity=2&_sessionid=SessionID&_sessionkey=NewSessionKey

    This statement will return two items matching your query, starting from the second item. Here again, the values for handle, position, quantity, sessionid and sessionkey have to be given without quotes.

  4. Close the cursor, using a command of the form:

    URLprefix/Collection?_cursor=close&_handle=1&_sessionid=SessionID&_sessionkey=...

The _define command

The _define command is used to create a new schema or a collection, or to modify an existing schema or collection. The collection and schema can be specified together in a schema definition file. In this case, the collection and / or schema(s) to be defined or updated have to be expressed in terms of the Tamino schema language. For more information on the Tamino schema language see the Tamino XML Schema User Guide.

In addition, the collection can be defined separately by using a collection definition document.

The _define command can also be used to define schema clusters, i.e. several schemas in a single command.

Defining a schema

The syntax for using a schema definition file is as follows:

URLprefix?_define=SchemaDefinition[&_mode=validate]

The input schema definition document defines both the schema and the collection to which it belongs. If the collection does not already exist, it is created automatically.

The option _mode=validate can be used for cases of schema evolution, i.e. where an existing schema is modified. For more information, refer to the section Schema Modifications in the Tamino XML Schema User Guide.

Defining a schema cluster

It is possible to define a schema cluster, i.e. two or more schemas with a single _define command. This can be useful if, for example, you wish to define several schemas that reference each other (cyclic schema definition). Tamino checks the schemas for completeness only after all of the schemas in the _define command have been processed. This means also that a schema that imports or includes other schemas can be defined together with the required import or include files with a single _define command; in this case, the order in which the schema definition and its import or include files are specified in the _define command is irrelevant. In addition, defining multiple related schemas in a single command is often more efficient, since many schema checks will only be performed once.

The syntax of this variant of the _define command is:

URLprefix?_define=$S1,$S2,...&$S1=SchemaDef1&$S2=SchemaDef2...

where $S1, $S2 etc. are placeholders for schema documents that follow later in the command, and SchemaDef1, SchemaDef2 etc. represent the actual schema definitions. The placeholders $S1, $S2 etc. can be any names consisting of 7-bit printable ASCII characters and must begin with a dollar character. Note that the placeholder names are not the names assigned to the schemas that will be created; the schema names and the names of any doctypes defined for the schemas are defined in the schema definitions SchemaDef1, SchemaDef2 etc.

There is no restriction to the number of schemas you can define in this way with a single _define command.

Defining a collection

The syntax for using a collection definition file is as follows:

URLprefix?_define=CollectionDefinition[&_mode=validate]

The structure of CollectionDefinition is as follows:

<tsd:collection name="CollectionName"
     xmlns:tsd="http://namespaces.softwareag.com/tamino/TaminoSchemaDefinition">
    <tsd:schema use ="Option"/>
</tsd:collection>

where CollectionName is the name of the collection and Option can have one of the following values:

Option Meaning

required (this is the default value)

Before a document can be stored in the collection, a schema describing the corresponding doctype must be defined explicitly.

optional

A schema is not necessary. If a schema describing a matching doctype is already defined, the document will be stored there. If no such schema exists, Tamino will store documents without a user-defined doctype.

prohibited

The explicit creation of a schema is not permitted. Tamino will store the documents without schema information.

For more information on how Tamino stores documents according to the option specified, see the description of the _process command below.

The value of the option can only be modified from "required" or "prohibited" to "optional".

The collection ino:etc uses the setting "optional".

Restriction for non-XML doctypes

If an existing schema for a non-XML doctype is being updated, the tsd:noConversion child element of the tsd:nonXML element of the doctype may only be added or removed if the doctype currently contains no documents.

The _delete command

The _delete command is used to delete database documents. You can use X-Query language expressions to select the document(s) to be deleted.

Example:

To delete the XML document of doctype patient and with document ID "4711" in the collection Hospital:

URLprefix/Hospital?_delete=patient[@ino:id="4711"]

Note:
You can also delete documents by using the update delete statement in an _xquery command.

The _destroy command

The _destroy command removes a query that was prepared using the _prepare command. The prepared query is specified by its handle. The following request shows an example that destroys the prepared query that has the handle 42:

URLprefix?_destroy=42&_sessionid=479356&_sessionkey=729661

See also the section Prepared Queries for more information about using prepared queries.

The _diagnose command

The _diagnose command is used to test the functionality of the outer X-Machine layers concerned with the HTTP handling (the HTTP connection layers).

The X-Machine command _diagnose works with HTTP GET and POST requests.

echo

URLprefix?_diagnose=echo

delivers the HTTP headers seen in the Tamino Server if X-Machine is reachable by the web server, otherwise an error message is generated by the web server.

ping

URLprefix?_diagnose=ping

tries to establish an HTTP connection and returns a positive answer in the case of success.

time

URLprefix?_diagnose=time

returns the total amount of CPU time that the server has been active in user mode (i.e. executing user requests) since the database server was started, and the total amount of CPU time that the server has been active in system (kernel) mode (i.e. executing system calls that result from user requests) since the database server was started. The values returned are the total times for all users together, not the individual times for each user.

version

URLprefix?_diagnose=version

returns the version of the Tamino Server.

The _disconnect command

The _disconnect command is used to finish the current session that was opened using a _connect command. If a transaction is still open, it is committed (i.e. the changes made during this transaction are stored in the database) before the session is closed.

Note:
For a summary of restrictions, see the section Transaction-Related Commands.

Example:

URLprefix?_disconnect=*&_sessionid=479356&_sessionkey=934482

The _execute command

The _execute command executes a prepared query, i.e. an XQuery query that has been precompiled using the _prepare command. A prepared query can be executed multiple times in the same session.

The syntax of the command is as follows.

URLprefix?_execute=Type&_handle=Handle

where Type is a text string that describes the type of operation to be executed, and Handle represents the handle that was returned when the query was prepared using the _prepare command.

Currently, Type can only take the value "prepared-xquery".

Example

URLprefix?_execute=prepared-xquery&_handle=42&_sessionid=479356&_sessionkey=358290

See also the section Prepared Queries for more information on prepared queries.

The _htmlreq command

The _htmlreq command is a special command for processing HTML forms. Refer to the document Tamino Forms Handler.

The _prepare command

The _prepare command precompiles an XQuery query. Such prepared queries can be executed multiple times at a later stage in the same session by using the _execute command. You can define any number of prepared queries in a session. Each prepared query is identified by a handle that is returned by Tamino when the _prepare command is issued. The prepared query exists for the duration of the current session; when a session terminates, all prepared queries of that session are deleted.

The _prepare command gets the XQuery string as argument. It returns a handle that identifies the prepared query within a session.

The syntax of the command is as follows.

URLprefix?_prepare=QueryStatement&_sessionid=SessionID&_sessionkey=SessionKey

where QueryStatement is the XQuery statement, SessionID is the current session ID and SessionKey is the session key returned by the previous command in the session.

An example request looks like:

URLprefix?_prepare=for $a in collection("bib") return $a&_sessionid=479356&_sessionkey=220815

Tamino returns a response that specifies the handle of the prepared query (in this example, the value of the handle returned is "42"):

<ino:query ino:handle="42"/>

See also the section Prepared Queries for more information on prepared queries.

The _process command

The _process command is used to insert one or more new documents into a Tamino database or to replace one or more existing documents. If more than one document is being inserted or replaced, the documents must be wrapped in ino:request and ino:object elements, using the format described in the section Input and Output File Formats of the Data Loader documentation. If a single document is being inserted or replaced, the use of the wrappers is optional.

The X-Machine converts XML documents to Unicode before storing them in Tamino.

Tamino does not always preserve the literal representation of XML documents. Also, entities are resolved.

When an XML document is retrieved from Tamino, the returned document is equivalent to the canonical form of the original document. For example, an empty element such as <br/> in a document stored into Tamino is returned in the canonically equivalent form <br></br>. Also, the order of multiple attributes given in an element's start tag may be altered.

Criteria for inserting or replacing a document

Tamino uses the values of the document ID and/or document name that can optionally be supplied in the input request to decide whether to insert a new document or replace an existing document. The rules governing this decision are as follows:

This can be summarized as follows:

Document name supplied? Document ID supplied? Document with this ID and/or name already exists? Resulting action
no no -

The document is inserted with no name. Tamino assigns an ID automatically.

This behaviour is different from the behaviour when using plain URL addressing, for which either the document name or the ID or both are required. See the section Criteria for inserting or replacing a document in the chapter Requests using Plain URL Addressing for details.

yes no yes The document with the given name is replaced.
no The document is inserted with the given name.
no yes yes The document with the given ID is replaced.
no Not permitted: if an ID is supplied, a document with this ID must already exist. An error is returned.
yes yes yes The document with the given name and ID is replaced.
no Not permitted: if a name and an ID are supplied in the same request, a document with this name and ID must already exist. An error is returned.

Specifying the document name

The document name can be specified in several ways:

If more than one way of supplying the name is used in the same request, the values given for the name must be identical, otherwise an error response will be returned.

Specifying the document ID

The document ID can be specified in several ways:

If more than one way of supplying the ID is used in the same request, the values given for the ID must be identical, otherwise an error response will be returned.

Storing new documents

You can store XML documents and non-XML documents into a Tamino database. Tamino decides whether a document is an XML document or a non-XML document depending on the MIME media type specified in the HTTP header. See the section Media Type Requirements for details.

If you do not specify a collection name, regardless of whether the document is an XML document or not, the document will be stored in the collection ino:etc.

For any XML document that will be stored in a collection, the root element must have the same expanded QName as the QName of an existing doctype. If there is no such doctype, an error will be returned in the X-Machine response document, unless the schema allows for schemaless storage. See the section The _define command for information on how to create such a collection. For information about QNames, see the section General Information on Namespaces in the document XML Namespaces in Tamino.

For a document that will be stored in a schemaless collection other than ino:etc, the behaviour is as follows:

Example

URLprefix/Collection?_process=XMLdocument

causes the specified XML document to be stored in the specified collection. The doctype is identified by the expanded QName of the XML document's root node.

Replacing existing documents

In general, Tamino offers two ways in which the contents of an existing document can be modified:

The _process command can be used to replace documents but not to update them. Updating a document is possible using the XQuery update command, as indicated in the section The _xquery command below and also in the section Performing Update Operations of the XQuery User Guide.

To replace an existing document, you need to address it by the document ID or document name that was assigned to it when the document was created, as described above in the section Criteria for inserting or replacing a document.

Example: replace by specifying the document ID on the root element

Assume that the patient Charles Dickens had been originally stored with the following data in the patient doctype of the Hospital collection:

<?xml version="1.0"?>
<patient>
  <name>
    <surname>Dickens</surname>
    <firstname>Charles</firstname>
  </name>
</patient>

and the response document contained the following data, specifying that the document ID "15" had been assigned to the new document:

<ino:object ino:collection="Hospital" ino:doctype="patient" ino:id="15" />

Then, to change the contents of this document, for example to change the contents of the element firstname from "Charles" to "Charlie", send a _process request with the new data, specifying ino:id="15" on the root element, for example:

<?xml version="1.0"?>
<patient ino:id="15">
  <name>
    <surname>Dickens</surname>
    <firstname>Charlie</firstname>
  </name>
</patient>

The _rollback command

The _rollback command is used to discard all of the database changes that were made during the current transaction. Supply the session ID that was returned at the start of the session, and the session key that was returned from the previous command.

If an active transaction has modified an external database via X-Node and receives a rollback request, a rollback is also issued on the external database.

Note:
For a summary of restrictions, see the section Transaction-Related Commands.

Example:

URLprefix?_rollback=*&_sessionid=479356&_sessionkey=340711

The _undefine command

The _undefine command is used to delete one or more existing collections, schemas or doctypes.

Warning:
When you delete a collection, schema or doctype, all documents and other data belonging to that collection, schema or doctype are also deleted.

Undefining collections, schemas and doctypes

The syntax of the command is as follows. Note that to delete a doctype it is also necessary to supply the name of the schema.

URLprefix?_undefine=Collection[/schema[/doctype]], ...

The name of the collection must be supplied as a parameter to the _undefine command. The name of a collection in the URLprefix, if present, is ignored.

In the same way as it is possible to use the _define command to define schema clusters, you can use the _undefine command to delete schema clusters. Thus, for example, you can use a single _undefine command to delete several schemas that reference each other, without leaving the remaining Tamino schema definitions in an inconsistent state (see the following examples).

Collections whose names start with the characters "ino:" cannot be deleted via _undefine; these are reserved for internal use in Tamino.

Examples

To delete the collection Hospital, specify :

URLprefix?_undefine=Hospital

To delete the schema HospitalSchema and all its defined doctypes from the collection Hospital, specify:

URLprefix?_undefine=Hospital/HospitalSchema

To delete the doctype patient in the schema HospitalSchema in the collection Hospital, specify:

URLprefix?_undefine=Hospital/HospitalSchema/patient

To delete the collection Schools, the schema HospitalSchema in collection Hospital and the doctype Cars in schema ResourceSchema in collection Transport, specify:

URLprefix?_undefine=Schools,Hospital/HospitalSchema,Transport/ResourceSchema/Cars

The _xql command

The _xql command performs a database query to retrieve XML documents, using the X-Query query language. X-Query is described in detail in the document X-Query User Guide.

Note:
Certain characteristics of the documents or nodes returned in the query response document can vary from those returned by requests that use plain URL addressing. In particular, the following points apply to the query response that do not apply to plain URL addressing: (a) a response wrapper is returned (b) the pseudo-attributes ino:id and ino:docname (if defined) are returned (c) the XML prolog is not delivered.

Example

To retrieve the list of surnames of all patients in the doctype patient of the collection Hospital, use the following:

URLprefix/Hospital/patient?_xql=patient/name/surname

X-Query search modes

By default, locks are set on all required indexes while an X-Query request is processing them. This ensures that if a query needs to scan several indexes, the query runs in an atomic way, i.e. no concurrent X-Machine command can alter any of the indexes while the query is processing them. This behaviour can sometimes lead to a situation that the indexes are locked for a relatively long time, for example:

While the indexes are locked, no new update/insert/delete requests can be processed, because of course they must wait until the index locks are removed. However, if new read requests arrive while update/insert/delete requests are queued, Tamino queues them behind the update/insert/delete requests. This ensures that the update/insert/delete requests are not kept permanently waiting by newly-arriving read requests that might again require index locks. So a situation can arise whereby one or more relatively simple read requests have to wait a long time in a queue due to the index locks.

For performance reasons, an application might not require the index locks to be set in the way described. By removing this restriction, query results can become slightly inaccurate in some cases if concurrent requests are performing update/insert/delete operations, but this might not be critical for the application.

The optional parameter _querysearchmode specifies whether an X-Query request will run in an atomic way, i.e. setting index locks until the request completes, or whether it is acceptable for concurrent requests to access and possibly modify the indexes while the X-Query request is running.

The parameter _querysearchmode extends the _xql command syntax as follows.

_xql=QueryString&_querysearchmode=ModeValue

where QueryString is the X-Query query definition and ModeValue takes one of the values shown in the following table:

Parameter value Meaning
_querysearchmode=accurate All indexes required by the X-Query request are locked. This is the default behaviour.
_querysearchmode=approximate Indexes required by the X-Query request are not locked.
_querysearchmode=nonserialized Same as approximate, but additional postprocessing is omitted

The use of either _querysearchmode=approximate or _querysearchmode=nonserialized has advantages and disadvantages:

The Tamino-specific HTTP header field X-INO-querySearchMode can be used in the HTTP header to pass a value for the query search mode. This can only be done for requests that contain an X-Query command (i.e. requests in which the _xql command is used). The effect of X-INO-querySearchMode is restricted to the single HTTP request that contains it. It cannot be used on a _connect command to set a default for the entire user session.

Note:
If the parameter _querysearchmode and the HTTP header field X-INO-querySearchMode are both supplied, X-INO-querySearchMode takes precedence over _querysearchmode.

The format of the field X-INO-querySearchMode is as follows:

X-INO-querySearchMode: QueryMode

where QueryMode can be any one of the allowed ModeValue values of the _querysearchmode parameter, for example:

X-INO-querySearchMode: approximate

The _xquery command

The _xquery command performs a database query using the language XQuery, to retrieve XML documents and optionally update or delete them. XQuery is described in detail in the document XQuery User Guide

Note:
Certain characteristics of the documents or nodes returned in the query response document can vary from those returned by requests that use plain URL addressing. In particular, the following points apply to the query response that do not apply to plain URL addressing: (a) a response wrapper is returned (b) the XML prolog is not delivered.

Examples

Example 1

To find all documents in which the patient's name is "Atkins" in the doctype patient in the collection Hospital, and for each occurrence return a new document containing the surname and firstname in a "result" element, use the following URL:

URLprefix/Hospital?_xquery=
for $p in input()/patient
where $p/name/surname="Atkins"
return  <result>{$p/name/surname},{$p/name/firstname}</result>

Here, "input()/patient" delivers a list of patient root elements. The return statement delivers an element such as the following for each document that matches the query:

<result>Atkins,Paul</result>

Example 2

To delete all documents in which the patient's name is "Atkins" in the doctype patient in the collection Hospital, use the following URL (shown here split across several lines for better readability):

URLprefix/Hospital?_xquery=
update
for $p in input()/patient
where $p/name/surname="Atkins"
delete $p/..

Here, "input()/patient" delivers a list of patient root elements. However, documents can only be deleted by deleting the document node rather than the root element, therefore "$p/.." must be specified in the delete statement to address the document node which is the parent node of the root element.

For _xquery, cursor locks are held until the cursor's transaction is committed or aborted.

Serialization of Response Document

The result of every query performed with _xquery is a sequence of elements. By default, the returned documents are enclosed in a wrapper xq:result element.

If a direct serialization of a returned node type is not possible, an element wrapper will be used, as follows:

Search Modes

Similar to query search modes available for _xql, you can change the search modalities for an XQuery request in order to improve speed. This only affects dirty read transactions, i.e. _isolationLevel is set to "uncomittedDocument" or _lockMode is set to "unprotected". In all other cases the server returns an error. It is also an error to use it for _xquery update commands.

If no _querysearchmode parameter is used, _querysearchmode=accurate is assumed.

You can use _querysearchmode=approximate for XQuery requests executed in streaming mode, i.e. every document access involves at most one and only one index scan. Using _querysearchmode=approximate has the same effect as described above for X-Query requests including a possible postprocessing phase. Prepared queries are implicitly recompiled before execution in case the _querysearchmode parameter value has changed. If you add the explain directive to the query prolog in order to analyze query processing it is indicated whether this query can be processed in streaming mode. A warning is returned when _querysearchmode=approximate is specified but not applicable.

Queries that cannot be processed in streaming mode, e.g. because they need to access multiple indexes and documents, require locks during the entire query execution in order to guarantee a consistent result. An example illustrates what could happen when locks are not in place the whole time:

Assume there is a doctype Person with an ID attribute, together with an element spouse whose ID attribute stores the value of the married person and elements children with an ID attribute as well. Let us further assume that persons have only children with their spouses. Then a query could ask for a (female) person, her children, her husband and the number of her husband's children. While executing this query the woman's first child is returned, but has not yet been added to the father. As a result, the query returns the woman, its child, the father, and the information that he has no children.

Using _querysearchmode=nonserialized it is possible to force query processing without locks, thus improving performance and request throughput, but at the cost of inaccurate query results: Having no locks could lead to a situation that a query accesses a document multiple times, but discovers that the document has changed or even been deleted since the last access. In this case there is no meaningful result for this query and the error INOXQE6312 will be returned instead.

As with _querysearchmode=approximate prepared queries are implicitly recompiled before execution in case the _querysearchmode parameter value has changed. Furthermore, _querysearchmode=nonserialized can also be used for queries in streaming mode.

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X-Machine Command Options

Duration Measurement

The _duration command can be used in conjunction with one or more other X-Machine commands and causes timing information about the other commands to be returned in the response document. Currently it takes one value which must be set to "on", otherwise it will be ignored.

The syntax of the command is as follows.

URLprefix?OtherCommands?_duration="on"

where OtherCommands represents one or more X-Machine commands for which the timing information is to be returned.

When _duration="on" is specified, the response document contains an ino:time element that contains the following attributes:

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Syntax of XML Responses

Responses to X-Machine commands are delivered as XML documents that combine context information (optional), result information (optional), and message information (optional) in a Tamino-defined wrapper. Normally, this wrapper has to be parsed by the client that issued an XML command to the X-Machine. The attributes and elements that may occur in a response document are preceded with the namespace prefix string "ino:" to indicate XML constructs from the Tamino namespace http://namespaces.softwareag.com/tamino/response2.

Note:
The response wrapper cannot be suppressed by using X-Machine command options. However, certain commands have options to suppress the response wrapper. See the section Suppressing the Tamino Response Wrapper for further information.

In general, the success or failure of the client request is indicated in the ino:returnvalue attribute of the ino:message element of the response document. A value of 0 indicates a successful response, whereas a non-zero value indicates either an error or a non-standard response.

If you use the Tamino Interactive Interface with an XML-capable browser, the response document from the X-Machine is displayed in a separate frame of the browser. This is a very useful way of becoming acquainted with the typical response documents that the X-Machine returns for the various X-Machine commands.

Tip:
The schema for the response document is available for reference in XML Schema format in the file TaminoResponse.xsd in the directory Files/schemas under the Tamino installation directory.

Below are examples of the X-Machine responses for various commands.

Example of a response to the _connect command

When a session is started using the _connect command, the response document has the following structure:

<?xml version="1.0" encoding="iso-8859-1" ?>
<ino:response xmlns:ino="http://namespaces.softwareag.com/tamino/response2"
 xmlns:xql="http://metalab.unc.edu/xql/" ino:sessionid="2" ino:sessionkey="30381">
  <ino:message ino:returnvalue="0">
    <ino:messageline>_CONNECT: session 2 established</ino:messageline>
  </ino:message>
</ino:response>

Example of a response to the _define command

When a doctype is defined using the _define command, the response document has the following structure (the example assumes the doctype to be in the schema HospitalSchema in the collection Hospital):

<?xml version="1.0" encoding="iso-8859-1" ?>
<ino:response xmlns:ino="http://namespaces.softwareag.com/tamino/response2"
 xmlns:xql="http://metalab.unc.edu/xql/">
  <ino:message ino:returnvalue="0">
    <ino:messageline>_DEFINE: schema HospitalSchema in collection Hospital defined</ino:messageline>
  </ino:message>
</ino:response>

If the collection to which the schema belongs did not already exist, it is created automatically when the schema is defined. There is no additional X-Machine response to confirm this.

Example of a response to an updating _define command

When a schema is updated using the _define command, the response document has the following structure (the example assumes that the schema HospitalSchema in the collection Hospital is being updated):

<?xml version="1.0" encoding="iso-8859-1" ?>
<ino:response xmlns:ino="http://namespaces.softwareag.com/tamino/response2"
 xmlns:xql="http://metalab.unc.edu/xql/">
  <ino:message ino:returnvalue="0">
    <ino:messageline>_DEFINE: schema HospitalSchema in collection Hospital updated successfully
    </ino:messageline>
  </ino:message>
</ino:response>

Example of a response to the _delete command

When an XML document is deleted using the _delete command, the response document has the following structure:

<?xml version="1.0" encoding="iso-8859-1" ?>
<ino:response xmlns:ino="http://namespaces.softwareag.com/tamino/response2"
 xmlns:xql="http://metalab.unc.edu/xql/">
  <ino:message ino:returnvalue="0">
    <ino:messageline>_DELETE: document(s) deleted</ino:messageline>
  </ino:message>
</ino:response>

If no documents were found that matched the delete request, the following structure is returned:

<?xml version="1.0" encoding="iso-8859-1" ?>
<ino:response xmlns:ino="http://namespaces.softwareag.com/tamino/response2"
 xmlns:xql="http://metalab.unc.edu/xql/">
  <ino:message ino:returnvalue="8300">
    <ino:messagetext ino:code="INOXIE8300">No matching document found</ino:messagetext>
  </ino:message>
</ino:response>

Examples of responses to the _diagnose command

The command ?_diagnose=ping returns a response document with the following structure:

<?xml version="1.0" encoding="ISO-8859-1" ?>
<ino:response xmlns:ino="http://namespaces.softwareag.com/tamino/response2"
 xmlns:xql="http://metalab.unc.edu/xql/">
  <ino:request>
    <ino:diagnose ino:request-type="ping" />
  </ino:request>
  <ino:message>
    <ino:messageline ino:subject="Server">is alive</ino:messageline>
  </ino:message>
</ino:response>

The command ?_diagnose=echo returns a response document with the following structure:

<?xml version="1.0" encoding="ISO-8859-1" ?>
<ino:response xmlns:ino="http://namespaces.softwareag.com/tamino/response2"
              xmlns:xql="http://metalab.unc.edu/xql/">
  <ino:request>
    <ino:diagnose ino:request-type="echo"/>
  </ino:request>
  <ino:message>
    <ino:messageline ino:subject="Authenticated User ID"></ino:messageline>
    <ino:messageline ino:subject="Authentication Type"></ino:messageline>
    <ino:messageline ino:subject="Request Method">GET</ino:messageline>
    <ino:messageline ino:subject="Client's IP address">127.0.0.1</ino:messageline>
    <ino:messageline ino:subject="Client's DNS name"></ino:messageline>
    <ino:messageline ino:subject="Webserver's hostname">mypc.mycompany.com</ino:messageline>
    <ino:messageline ino:subject="Server Software">Apache/2.0.54 (Win32)</ino:messageline>
    <ino:messageline ino:subject="User-Agent">Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.16) 
                                              Gecko/20080702 Firefox/2.0.0.16</ino:messageline>
    <ino:messageline ino:subject="Accept-Charset">ISO-8859-1,utf-8;q=0.7,*;q=0.7</ino:messageline>
    <ino:messageline ino:subject="Accept-Language">en-us,en;q=0.5</ino:messageline>
    <ino:messageline ino:subject="TransportService">XTS</ino:messageline>
  </ino:message>
</ino:response>

The command ?_diagnose=version returns a response document with the following structure:

<?xml version="1.0" encoding="ISO-8859-1" ?>
<ino:response xmlns:ino="http://namespaces.softwareag.com/tamino/response2"
 xmlns:xql="http://metalab.unc.edu/xql/">
  <ino:request>
    <ino:diagnose ino:request-type="version" />
  </ino:request>
  <ino:message>
    <ino:messageline ino:subject="Version">n.n.n.n</ino:messageline>
  </ino:message>
</ino:response>

where "n.n.n.n" is the Tamino version number.

The command ?_diagnose=time returns a response document with the following structure:

<?xml version="1.0" encoding="ISO-8859-1" ?>
<ino:response xmlns:ino="http://namespaces.softwareag.com/tamino/response2"
 xmlns:xql="http://metalab.unc.edu/xql/">
  <ino:request>
    <ino:diagnose ino:request-type="time" />
  </ino:request>
  <ino:message>
    <ino:messageline ino:subject="User Time" ino:unit="100ns">18626784</ino:messageline>
    <ino:messageline ino:subject="Kernel Time" ino:unit="100ns">14520880</ino:messageline>
  </ino:message>
</ino:response>

Example of a response to the _duration command

The following structure is an example of the X-Machine response when timing information is requested for the query "count(*)" on a set of test data:

<?xml version="1.0" encoding="ISO-8859-1" ?>
<ino:response xmlns:ino="http://namespaces.softwareag.com/tamino/response2"
              xmlns:xql="http://metalab.unc.edu/xql/">
  <xql:query>count(*)</xql:query>
  <ino:message ino:returnvalue="0">
    <ino:messageline>XQL Request processing</ino:messageline>
  </ino:message>
  <xql:result>11</xql:result>
  <ino:message ino:returnvalue="0">
    <ino:messageline>XQL Request processed</ino:messageline>
   </ino:message>
  <ino:time ino:date="2004-01-23" ino:time="13:48:09.218" ino:duration="2" />
</ino:response>

Example of a response to the _process command

The following structure is an example of the X-Machine response when an document is stored in the user-defined doctype patient in the collection Hospital:

<?xml version="1.0" encoding="iso-8859-1" ?>
<ino:response xmlns:ino="http://namespaces.softwareag.com/tamino/response2"
 xmlns:xql="http://metalab.unc.edu/xql/">
  <ino:message ino:returnvalue="0">
    <ino:messageline>document processing started</ino:messageline>
  </ino:message>
  <ino:object ino:collection="Hospital" ino:doctype="patient" ino:id="3" /> 
  <ino:message ino:returnvalue="0">
    <ino:messageline>document processing ended</ino:messageline> 
  </ino:message>
</ino:response>

Example of a response to the _undefine command

When a schema is deleted using the _undefine command, the response document has the following structure:

<?xml version="1.0" encoding="iso-8859-1" ?>
<ino:response xmlns:ino="http://namespaces.softwareag.com/tamino/response2"
 xmlns:xql="http://metalab.unc.edu/xql/">
  <ino:message ino:returnvalue="0">
    <ino:messageline>_UNDEFINE: schema deleted</ino:messageline>
  </ino:message>
</ino:response>

When a collection is deleted using the _undefine command, the response document has the following structure:

<?xml version="1.0" encoding="iso-8859-1" ?>
<ino:response xmlns:ino="http://namespaces.softwareag.com/tamino/response2"
 xmlns:xql="http://metalab.unc.edu/xql/"> 
  <ino:message ino:returnvalue="0">
    <ino:messageline>_UNDEFINE: collection deleted</ino:messageline>
  </ino:message>
</ino:response>

Example of a response to the _xql command

The following response is returned following the query

URLprefix/Hospital?_xql=patient/name/surname

which retrieves the surname children of the name elements of the patient doctype in the collection Hospital. The full list of the surnames has been limited here to 2 surnames for display purposes. Note that the actual result of the query is the content of the xql:result element.

<?xml version="1.0" encoding="ISO-8859-1" ?> 
<ino:response xmlns:ino="http://namespaces.softwareag.com/tamino/response2" 
  xmlns:xql="http://metalab.unc.edu/xql/">
  <xql:query>patient/name/surname</xql:query> 
  <ino:message ino:returnvalue="0">
    <ino:messageline>XQL Request processing</ino:messageline> 
  </ino:message>
  <xql:result>
    <surname ino:id="1">Atkins</surname> 
    <surname ino:id="2">Bloggs</surname> 
  </xql:result>
  <ino:message ino:returnvalue="0">
    <ino:messageline>XQL Request processed</ino:messageline> 
  </ino:message>
</ino:response>

If no document matches the query, the following structure is returned (the example assumes that a search was done for the surname "xxxx", and that this surname does not exist):

<?xml version="1.0" encoding="ISO-8859-1" ?>
<ino:response xmlns:ino="http://namespaces.softwareag.com/tamino/response2"
xmlns:xql="http://metalab.unc.edu/xql/">
  <xql:query>patient[name/surname="xxxx"]</xql:query>
  <ino:message ino:returnvalue="0">
    <ino:messageline>XQL Request processed, no object returned</ino:messageline>
  </ino:message>
</ino:response>

Example of a response to the _xquery command

The following response is returned following the query

URLprefix/Hospital?_xquery=for $p in input()/patient
return  <result>{$p/name/surname}</result>

which retrieves the surname children of the name elements of the patient doctype in the collection Hospital. The full list of the surnames has been limited here to 2 surnames for display purposes. Note that the actual result of the query is the content of the xql:result element.

<?xml version="1.0" encoding="windows-1252" ?>
<ino:response xmlns:ino="http://namespaces.softwareag.com/tamino/response2"
xmlns:xql="http://metalab.unc.edu/xql/">
  <xq:query xmlns:xq="http://namespaces.softwareag.com/tamino/XQuery/result">
    <![CDATA[
    for $p in input()/patient
    return  <result>{$p/name/surname}</result>
    ]]>
  </xq:query>
  <ino:message ino:returnvalue="0">
    <ino:messageline>XQuery Request processing</ino:messageline>
  </ino:message>
  <xq:result xmlns:xq="http://namespaces.softwareag.com/tamino/XQuery/result">
    <result>
      <surname>Atkins</surname>
    </result>
    <result>
      <surname>Bloggs</surname>
    </result>
  </xq:result>
  <ino:message ino:returnvalue="0">
    <ino:messageline>XQuery Request processed</ino:messageline>
  </ino:message>
</ino:response>

If no document matches the query, the following structure is returned (the example assumes that a search was done for the surname "xxxx", and that this surname does not exist):

<?xml version="1.0" encoding="ISO-8859-1" ?>
<ino:response xmlns:ino="http://namespaces.softwareag.com/tamino/response2"
  xmlns:xql="http://metalab.unc.edu/xql/">
  <xq:query xmlns:xq="http://namespaces.softwareag.com/tamino/XQuery/result">
    <![CDATA[
    for $p in input()/patient
    where $p/name/surname="xxxx"
    return  <result>{$p/name/surname}</result>
    ]]>
  </xq:query>
  <ino:message ino:returnvalue="0">
    <ino:messageline>XQuery Request processing</ino:messageline>
  </ino:message>
  <xq:result xmlns:xq="http://namespaces.softwareag.com/tamino/XQuery/result" />
  <ino:message ino:returnvalue="0">
    <ino:messageline>XQuery Request processed</ino:messageline>
  </ino:message>
</ino:response>

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Elements and Attributes in Tamino Response Documents

The following table shows commonly occurring elements and attributes in Tamino response documents.

Name

Element (E) or Attribute (A)

Purpose
ino:collection A Name of a collection
ino:current E Indicates the current cursor position in a result fetch set and the number of documents returned
ino:cursor E Cursor segment in a response block, describing parameters for the hit lists from query responses.
ino:database E Name of a database
ino:date A

Contains the date on which the _duration command was executed.

ino:diagnose E

Contains the value of the _diagnose keyword that was originally submitted to Tamino

ino:doctype A Name of a doctype
ino:duration A

Contains the duration of the command(s) for which the _duration command was specified.

ino:id A Document ID
ino:handle A

The handle number of an open cursor

ino:message E Message block
ino:messageline E Message line in plain text
ino:messagetext E Diagnostic text or error message text
ino:next E Indicates the next cursor position in a result fetch set
ino:object E Summarizes a document that was successfully stored. Attributes of this element could describe, for example, the collection and doctype into which a new document was stored.
ino:position A

Indicates the position in the result fetch set

ino:prev E Indicates the previous cursor position in a result fetch set
ino:quantity A

Indicates the number of documents returned from the result fetch set

ino:request E Summarizes the original client request to Tamino
ino:response E Top-level wrapper element for the response document
ino:returnvalue A Return code from XML retrieval
ino:sessionid A Session ID of a Tamino XML session, will remain unchanged during a session (which lasts from a _connect until a _disconnect command)
ino:sessionkey A Session key of a command sub-transaction inside a Tamino XML session
ino:time E, A

Element resulting from a _duration command, containing date, time and duration information. Also the attribute within the ino:time element that contains the time at which the _duration command was executed.

xq:query E

Contains the XQuery query that was submitted to Tamino

xq:result E Wrapper element for the XQuery query result
xql:query E

Contains the X-Query query that was submitted to Tamino

xql:result E Wrapper element for the X-Query query result

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Suppressing the Tamino Response Wrapper

In general, the response wrapper cannot be suppressed by using X-Machine Programming commands. However, various possibilities exist for suppressing the response wrapper for queries and server extensions. These possibilities are discussed in this section.

For related information on the response wrapper, see the section Syntax of XML Responses.

Suppressing the response wrapper in XQuery commands

There is an option available in the syntax of the _xquery command for suppressing the response wrapper for XQuery commands. It is described in the XQuery User Guide in the section Suppressing the Response Wrapper.

Suppressing the response wrapper in X-Query commands

There is no option available in the syntax of the _xql command for suppressing the response wrapper for X-Query queries. However, if the _xql command is of the form:

_xql=queryFunction(expression)

where queryFunction is a server extension acting as an output handler, and the code of queryFunction includes a server extension callback that sets the media type of the response document, then the response wrapper of the _xql command is suppressed implicitly. This is summarized in the section Suppressing the response wrapper by setting the media type.

The query function must be specified in the _xql request on the root level and must not contain a union or any other top-level binary operator. Therefore, the following examples are NOT allowed:

_xql=doctype[queryFunction(expression)]
_xql=queryFunction(expression1)|queryFunction(expression2)

Suppressing the response wrapper by setting the media type

It is possible to use the system callback SxsSetProperty with the property SX_PROPERTY_RSP_MEDIATYPE to set the media type of the response document. If a server extension that is used as an output handler for a query (XQuery or X-Query) uses this callback, this implicitly causes the response wrapper to be suppressed. For further information on setting the media type see the section Callback method SxsSetProperty in the X-Tension documentation.

Restrictions for suppressing the response wrapper

The response wrapper can only be suppressed in the ways indicated above if the following criteria are met:

Error Handling

If an error occurs during the execution of a request whose response wrapper has been suppressed, an error text will be appended to the response written up to that point. The error will be wrapped in the standard error markup (<ino:message>, <ino:messagetext> etc.).

Further information

If a response with a suppressed wrapper is being returned within a session, the session ID and session key are passed in the HTTP response header. See the section The HTTP header fields X-INO-Sessionid and X-INO-Sessionkey for details of the response header fields.

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Transaction-Related Commands

On Windows and UNIX, Tamino provides support for a two-phase commit protocol in the Tamino API for Java. Additionally, on Windows, Tamino provides support for a two-phase commit protocol in the programming APIs for Microsoft .NET and ActiveX. The two-phase commit protocol allows distributed transactions to be implemented, in which a transaction can relate to more than one database. When the two-phase commit protocol is not used or not available, a transaction can relate to a single database only. Refer to the documents Tamino API for Java, Tamino API for .NET and HTTP Client API for ActiveX in the Tamino documentation set for details of distributed transactions.

If Tamino accesses Adabas databases via X-Node, then transactions are started automatically on the X-Node database. These are closed with a commit or rollback when the Tamino transaction completes.

The following information is available for transaction-related commands:

For more information on transaction processing, see the document Transactions Guide.

Summary of Commands and Usage

The commands _connect, _commit, _rollback and _disconnect are needed to perform transaction processing using X-Machine commands.

A typical transaction sequence is:

  1. Start a new session by using the X-Machine _connect command. The response from the X-Machine for this command contains two attributes only delivered within a session, namely ino:sessionid for a unique session ID for the new session and ino:sessionkey for a key describing the current command.

  2. Issue some commands against X-Machine, e.g. _define, _process to define a schema and load data. These "normal" commands must be accompanied by the _sessionid and _sessionkey information in order to maintain the transaction continuity. This implies a request with at least three keyword/value pairs. The order is not important, therefore we may assume the following syntax for an X-Machine request during a transaction:

    URLprefix?Command=Data&_sessionid=SessionID&_sessionkey=SessionKey
  3. Finish the transaction by either:

    Discarding the previous changes using the _rollback command:

    URLprefix?_rollback=*&_sessionid=SessionID&_sessionkey=SessionKey

    Or finishing the transaction by committing the previous changes:

    URLprefix?_commit=*&_sessionid=SessionID&_sessionkey=SessionKey
  4. Perform other transactions as required by repeating steps 2 and 3.

  5. Close the session with the _disconnect command:

    URLprefix?_disconnect=*&_sessionid=SessionID&_sessionkey=SessionKey

Restrictions

On platforms where distributed transactions are supported using two-phase commit, the following commands are not allowed within a distributed transaction:

For the _disconnect command, the following additional restriction applies:

The HTTP header fields X-INO-Sessionid and X-INO-Sessionkey

Instead of the _sessionid and _sessionkey parameters, the X-Machine request may also specify the HTTP header fields X-INO-Sessionid and X-INO-Sessionkey in the request header. This feature is especially important in conjunction with plain URL addressing which does not allow specifying the _sessionid and _sessionkey parameters.

If an X-Machine request contained a _connect command or successfully continued in a previously established session context by passing a session ID and session key, it will return the session ID and the new session key to be used in the subsequent request in the following ways:

This method of returning this information will only be used if the response is embedded into an <ino:response> wrapper element. See the example in the section Example of a response to the _connect command. On the other hand, when using plain URL addressing, there is no response wrapper and the new session context will only be returned in the HTTP response header.

If a request containing an invalid session context is received by the X-Machine, one of the following will happen:

If both the HTTP header field X-INO-Sessionid and the parameter _sessionid are specified in the request, an error will be reported if they are inconsistent. If both the HTTP header field X-INO-Sessionkey and the parameter _sessionkey are specified in the request, only X-INO-Sessionkey will be processed. If X-INO-Sessionkey is valid, the _sessionkey parameter is ignored.

Session Parameters

There are additional session parameters that can be specified when a session is started with the _connect command. They are specified in the _connect command as additional keyword/value pairs. The available session parameters are:

The _isolationLevel Parameter

This parameter, together with the _lockMode parameter, specifies in what way two or more transactions in a session context can access the same data simultaneously. The _isolationLevel parameter can also be specified on requests in a non-session context, since such requests represent self-contained transactions.

For a detailed description of the isolation level and lock mode settings with examples, refer to the Transactions Guide document.

The interaction between the _isolationLevel and _lockMode parameters is described in the section The _lockMode Parameter below.

The parameter can have the following values:

In a session context, the default is _isolationLevel=stableDocument. In a non-session context, the default is _isolationLevel=uncommittedDocument, except for XQuery update commands, for which the default is _isolationLevel=committedCommand.

The value of _isolationLevel cannot be changed within a transaction.

The available isolation levels are described in the following sections.

_isolationLevel=uncommittedDocument

A command within a transaction with this isolation level can read a so-called dirty document at any time, which means that a concurrent transaction has changed or stored the document but might abort later on. The document content might be outdated in the sense that a concurrent transaction has changed the content after the current transaction has read it.

A command can also modify a document if no concurrent transaction is modifying the document, or no other transaction need the document in a stable state (isolation level stableCursor and stronger).

In this isolation level, the commands _delete and _process are executed as if they were in isolation level "committedCommand" (see below).

XQuery update commands with this isolation level are not possible. In such a case, the command is rejected with a response code 8552.

_isolationLevel=committedCommand

A command within a transaction in this isolation level can read documents that have been modified, inserted or updated by committed transactions but not documents that have been modified, inserted or updated by concurrent non-committed transactions.

_isolationLevel=stableCursor

A transaction with this isolation level guarantees that a document in the cursor result set will not be changed by a concurrent transaction (i.e. will still match the query predicate) in the following cases:

_isolationLevel=stableDocument

This isolation level guarantees that a document that has been read within the current transaction cannot be changed by a concurrent transaction until the end of the current transaction. This isolation level does not guarantee repeatable query results, i.e. a concurrent transaction can create another document that matches the search criteria of a query in the current transaction, so that if the query is issued twice in the same transaction the results can be different.

_isolationLevel=serializable

This isolation level guarantees that the result set of a query and in consequence the database changes made by the commands _process, _delete and update statement of _xquery cannot be influenced by concurrent transactions.

Effect of isolation level on concurrent transaction

The following table shows how the setting of the isolation level affects two concurrent transactions that try to access the same data. A transaction in session S1 is already accessing data that a transaction in session S2 now tries to access. S1 can be at any of three stages: (1) the data has been read but not yet written or committed (2) the data has been written but not yet committed (3) the data has been committed.

S1 current status S1 isolation level S2 permitted actions
data read but not yet written uncommittedDocument S2 can read and write the data
committedCommand S2 can read and write the data
stableCursor S2 can read data but cannot write it as long as the data is in the result set of an open cursor
stableDocument S2 can read the data
serializable S2 can read the data
data written but not yet committed (any isolation level) S2 can read the data with isolation level set to uncommittedDocument only
data committed (any isolation level) S2 can read the data regardless of the isolation level set for S2

The _lockMode Parameter

This parameter, together with the _isolationLevel parameter, specifies in what way two or more transactions in a session context can access the same data simultaneously. The _lockMode parameter can also be specified on requests in a non-session context, since such requests represent self-contained transactions. If one transaction is currently accessing data from the database and a second transaction attempts to access or modify the same data, the setting of the_lockMode and _isolationLevel parameters for each of the transactions determines whether access is possible for the second transaction.

For a detailed description of the isolation level and lock mode settings with examples, refer to the Transactions Guide document.

The locking of documents, doctypes and collections is controlled mainly by the setting of the _isolationLevel parameter. The _lockMode parameter gives advanced users additional possibilities for controlling the locking behaviour. Using _lockMode, it is possible to override the locking behaviour that has been defined by the _isolationLevel parameter. If you set the value of _lockMode to one of the valid values as described below, you set or remove locks on documents regardless of the setting of the _isolationLevel parameter.

The default behaviour for locking is defined by the _isolationLevel parameter. For this reason, there is no default value for _lockMode.

The _lockMode parameter can also be specified in a non-session context on a single command. This controls the behaviour of the command if it accesses data that is currently under the control of a transaction from another session or another command using the parameter in a non-session context.

The parameter can have the following values:

Since each of the concurring transactions or non-session commands specifies its own value for the parameter, there is a combined effect that is best described using an example.

The following example assumes that there are two sessions, namely S1 and S2, and a transaction in S1 is already accessing data that a transaction in S2 now tries to access. S1 can be at any of three stages in the transaction: (1) the data has been read but not yet written or committed (2) the data has been written but not yet committed (3) the data has been committed.

S1 current status S1 current lock mode S2 permitted actions
data read but not yet written (no value specified) S2 can access the data according to the value of the isolation level (see the isolation level table above)
unprotected S2 can access the data regardless of the S2 lock mode and isolation level settings
shared S2 can read the data regardless of the S2 lock mode and isolation level settings, but cannot write the data with any S2 lock mode setting and cannot read the data if the S2 lock mode is protected
protected S2 can only do a dirty read, with the lock mode set to unprotected or the isolation level set to uncommittedDocument
data written but not yet committed (any lock mode) S2 can only do a dirty read, with the lock mode set to unprotected or the isolation level set to uncommittedDocument
data committed (any lock mode) S2 can access the data regardless of the S2 lock mode and isolation level

The _lockMode parameter can be specified on every command.

The _lockWait Parameter

This parameter specifies which action to take if data is not accessible to the current transaction because another transaction has used the _isolationLevel or _lockMode parameter to restrict access to the data. The _lockWait parameter can also be specified on requests in a non-session context, since such requests represent self-contained transactions.

The _lockWait parameter can have the following values:

Parameter and value Meaning
_lockWait=yes If data is locked by a concurrent transaction, wait until the data is unlocked by the concurrent transaction and then continue processing.
_lockWait=no

If data is locked by a concurrent transaction, terminate the request immediately and return error message INOXYE9155 in the <ino:message> section of the response body.

Within a session context, the default value for the _lockWait parameter is "yes". In a non-session context, the default value is "no". The _lockWait parameter can be specified on every command.

The _maximumTransactionDuration parameter (previously named _transactionTimeout)

This parameter specifies the maximum length of time for which a transaction can be active before the Tamino server rolls back the currently active transaction. It overrides the Tamino server property maximum transaction duration for the current session.

This parameter only takes effect when specified in the _connect command. It can be specified for other commands but is ignored.

The parameter can have the following value:

Parameter and value Meaning

_maximumTransactionDuration=Value

This specifies the maximum time in seconds for which a transaction can be active. The minimum value is 20 and the maximum value is 2592000.

The _nonActivityTimeout parameter

This parameter specifies the maximum elapsed time (in seconds) that a transaction may be inactive. If this time is exceeded, the Tamino server rolls back the currently active transaction and also terminates the session. The value you specify overrides the value of the Tamino server property Non-Activity Timeout.

Note that the figure you specify for this parameter is only approximate. In any particular instance, the actual amount of time can vary from this value by up to 10 seconds.

The minimum value is 20, the default value is 900 and the maximum value is 2592000 (=30 days).

The _isolation Parameter (deprecated)

This parameter is provided for compatibility with Tamino Version 3 and is deprecated in the current version. In the current version it has been renamed to _lockMode. The permitted parameter values and their effects are the same as for the parameter _lockMode. In all new applications please use only _lockMode.

Comparison of Locking Mechanisms

The locking of documents, doctypes and collections is controlled mainly by the setting of the _isolationLevel parameter.

The _lockMode parameter gives advanced users additional possibilities for controlling the locking behaviour. Using this parameter, it is possible to override the locking behaviour that has been defined by the _isolationLevel parameter. If you set the value of _lockMode to one of the valid values as described above, you set or remove locks on documents regardless of the setting of the _isolationLevel parameter.

The default behaviour for locking is defined by the _isolationLevel parameter.

Default Parameters for Sessions, Transactions and Requests

The value given for the parameter _isolationLevel in the connect command at the beginning of a session is used as the default value of this parameter at the start of every transaction in the session. This value can be changed at the beginning of each transaction in the session by specifying a new value for the parameter, but the value reverts to the original default value at the start of every subsequent transaction. The parameter can be supplied on each request within a transaction, but in this case it must have the same value for every request in the transaction.

The values given for the parameters _lockMode, _isolation and _lockWait on the connect command at the beginning of a session are used as the default values of these parameters at the start of every request in every transaction in the session. New values for these parameters can be specified on every request, but the values revert to the original default values at the start of every subsequent request.

If a parameter is specified with no value, it is ignored.

Influence of Locking on Query Processing

During query processing, Tamino uses the defined indexes to select a set of documents that match the query. If no index is defined that can be used to process the query, Tamino temporarily locks all documents in the doctype until it has determined which documents match the query. When the set of documents that match the query has been determined, Tamino releases the locks on the documents that do not match the query.

This mechanism is necessary to ensure that no change can be made to any document in the doctype by a concurrent transaction while the query is being evaluated, since such a change to a document could affect whether or not the document matches the query, thereby causing Tamino to return inconsistent query results.

During query processing, Tamino can only lock all documents in a doctype if none of the documents is already locked by a concurrent transaction (that applies of course only for incompatible locks; if a read-lock is applied to a document, then further read-locks on the same document are allowed). This applies regardless of whether or not the documents locked by the concurrent transaction match the query. In such a case, the transaction that issues the query has to wait (if it has specified _lockWait=yes) until the concurrent transaction releases the lock, otherwise the request will be terminated with an error response but the transaction will continue.

If an index has been defined on a numeric element or attribute, it must be specified in the query predicate without quotes, otherwise Tamino will search for a string value instead of a numeric value. For example, the query predicate [@A=1] will search for documents in which the attribute A has the numeric value 1, whereas [@A="1"] will search for documents in which the attribute A has the string value "1". Since in this example the index contains only numeric values, Tamino cannot use the index to find documents that match the query, and will therefore proceed according to the method described above, locking all documents in the doctype while it searches for matching documents.

There is one exception to this rule: the value of the ino:id attribute in query predicates can be specified with or without quotes.

In query predicates that involve boolean operators, the presence of an index can also affect the number of documents that are locked by Tamino during query processing. Suppose for example that there is a schema with an element named A of type xs:integer with a standard index, and there can only be one occurrence of the element A in any document based on the schema. Let p be a predicate that cannot be evaluated using an index. For three queries with predicates "[A<5] and p", "[A>5] and p", "[A=5] and p", the index processor produces disjunct result sets, thus the queries do not create locking conflicts.

Effect of implicitly terminating a transaction

If a _disconnect command is issued while a transaction is pending or open, the transaction is automatically committed.

If a timeout, deadlock or journal overflow occurs while a transaction is pending or active, the transaction is rolled back.

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Prepared Queries

Queries expressed in XQuery can be precompiled once and executed many times in the same session. Such a query is called a prepared query. Each prepared query is identified by a handle that is returned by Tamino when the _prepare command is issued.

To create a prepared query, use the _prepare command.

To execute a prepared query, use the _execute command.

To delete a prepared query, use the _destroy command.

A prepared query can be defined with one or more so-called external variables (see below), which allows queries to be parameterized.

If a schema or security modification occurs while the session is active, prepared queries are recompiled automatically.

When a session terminates, the prepared query is no longer available.

External variables

In order to pass parameters to a query, XQuery provides external variables. The value of the external variable is determined when the query is executed using a _execute command. Thus any given prepared query can be used to execute different queries at different times in a session, depending on the values assigned to the external variables.

To pass a value to an external variable, the _execute command gets a key-value pair. The variable name is the key and the value holds the variable value. The variable value is specified by an XQuery expression.

An example is given by the following prepared query, in which the external variable $y is used as a placeholder for a value that will be provided in a subsequent _execute command:

declare variable $y as xs:integer external
input()/bib/book[@year = $y] 

The request to execute the prepared query looks like the following (assuming the handle of the prepared query to have the value "42"):

_execute=prepared-xquery&_handle=42&$y=2000 

which causes the following query to be executed:

input()/bib/book[@year = 2000]

This will for example return a list of all books published in the year 2000.

Currently there is no support for QName variables; this means that variables cannot be bound to a namespace.

All possible instances of the XQuery data model can be bound to an external variable. This means an external variable can be bound to simple type value, a node or a sequence of nodes and simple type values. To pass a sequence with more than a single item, sequence expressions can be used. The following request passes a sequence holding two xs:integers to the external variable $y of a prepared query:

_execute=prepared-xquery&_handle=42&$y=(xs:integer("2000"),xs:integer("2001")) 

The XQuery syntax also allows you to pass the integer values in the following way:

_execute=prepared-xquery&_handle=42&$y=(2000,2001) 

The following example show how computed attribute constructors can be used to pass an attribute node to an external variable:

_execute=prepared-xquery&_handle=42&$y=attribute year {"2000"}

To specify the value of external variables the following XQuery expressions can be used:

External variables in ordinary XQuery requests

External variables can be also passed to ordinary XQuery requests. For example:

_xquery=declare namespace xs=http://www.w3.org/2001/XMLSchema
declare variable $y as xs:integer external
input()/bib/book[@year = $y]
&$y=2000

Prepared queries and cursors

A cursor can use a prepared query by executing a command of the form:

_cursor=open&_execute=prepared-xquery&_handle=Handle[&$var1=Value1][&$var2=Value2]...

where Handle is the handle of the prepared query, as returned by the _prepare command, $var1, $var2 etc. are external variables used by the prepared query and Value1, Value2 etc. are the values to be assigned to the external variables.

Example

_cursor=open&_execute=prepared-xquery&_handle=42&y=2000

If a cursor is opened using the result set of a prepared query in this way, the same prepared query cannot be used in another concurrent cursor or separate _execute command until the cursor has been closed.

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Order of Execution of Commands

If several X-Machine commands, parameters or options are supplied in a single request, they are processed in a defined internal order, regardless of the order in which they appear in the request. The order is as follows:

  1. _sessionkey

  2. _sessionid

  3. _encoding

  4. _duration

  5. _isolationLevel

  6. _lockMode

  7. _isolation

  8. _lockWait

  9. _maximumTransactionDuration (previously _transactionTimeout)

  10. _nonActivityTimeout

  11. _scroll

  12. _count

  13. _handle

  14. _position

  15. _quantity

  16. _sensitive

  17. _connect

  18. _diagnose

  19. _admin

  20. _define

  21. _process

  22. _delete

  23. _cursor

  24. _xql

  25. _xquery

  26. _prepare

  27. _execute

  28. _destroy

  29. _htmlreq

  30. _undefine

  31. _commit

  32. _rollback

  33. _disconnect

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Interactive Environment for sending X-Machine Commands

To send commands interactively to the X-Machine, you can use the Tamino Interactive Interface, which is an HTML form.

Note:
If you have an XML-capable browser, the Tamino Interactive Interface displays the response document that the X-Machine sends in reply to each command.

For details, see the documentation for the Tamino Interactive Interface.

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