Creating a Mashup Script with EMML

For	Use These Elements or Attributes
Declaring Mashup and Macro Variables and Parameters	<variables>: contains one or more <variable> definitions to hold the input or output for any mashup script statement. <input>: defines an input parameter for this mashup. <output>: defines the name and type for the result of this mashup. Previous versions of EMML also used <inputparam> and <outputparam>. These declarations are deprecated.
Declaring Namespaces	xmlns attribute on <mashup> or <macro>: declares a namespace used by: A mashable information source called in the mashup. Macros called in the mashup. See Calling a Macro for more information. Presto extension statements. See EMML Namespaces for the namespace you must declare when you use Presto extensions such as <presto:presto-meta>. Parameters or variables constructed with literal XML. The <namespaces> element is deprecated.
Declaring Data Sources	<datasource>: defines connection information to one database for use with direct SQL statements in this mashup. You can also simply used named datasources defined in Presto.
Invoking Component Mashups and Mashables	<invoke>: invokes the operation for a published Presto mashable information source. See also Automatically Generating <invoke> Statements in Mashup Editor. <directinvoke>: Invokes an ungoverned, publically accessible web service or web site. Only HTML, Syndicated Feeds, REST web services and SOAP web services are supported. See also Controlling Component Mashup/Mashable Invocation at Runtime, Wrapping POJO Classes with Mashups and Web Clipping with a Mashup Script.
Issuing SQL Statements Directly to a Datasource	<sql>: to execute SQL queries to a datasource. <sqlUpdate>: to execute any other SQL statement to a datasource. <sqlcall>: to execute a stored procedure for a datasource. See also Handling or Throwing Exceptions.
Transforming Intermediate Results	<assign>: copies, and optionally transforms, one variable or variable fragment to another variable. This uses XPath 2.0 expressions to identify the source nodes to copy and optionally applies XPath functions to transform the result. This statement can also be used to assign literal values. <filter>: filters a set of nodes in a variable based on a filter expression in XPath 2.0. <group>: find unique values, and optionally filter, a set of repeating nodes in a variable. This constructs a result document based on those groups. This statement supports multiple levels of grouping and calculations on groups. <sort>: sorts a set of nodes in a variable based on sort keys and a sorting expression in XPath 2.0. <annotate>: adds attributes or children elements to a selected node of a variable and assigns values using an XPath expression. This is typically used to add data to the mashup result or an intermediate variable. <script>: defines a script to execute at runtime at the specified location in mashup processing. You can include JavaScript scripting code directly or point to an external file with any supported scripting language on the local server. The Presto Server supports JavaScript and Groovy as scripting languages inside mashup scripts. Scripting can also access any Java class in the classpath. <xslt>: process an input document using an XSLT stylesheet to tranform and construct a result document. See also Handling or Throwing Exceptions.
Combining Component Mashable or Mashup Results	<join>: joins the results of two or more mashable information sources or other mashups based on a join condition. This element works like a database join, where the results may be disparate but must have key nodes that determine how data is joined. You can also define the structure and nodes to include in the result of the join. <merge>: merges the results of two or more mashable information sources or other mashups that have homogenous result models. The element works like a database union. The results of all services must have identical structures.
Constructing the Mashup Result, Inputs or Intermediate Variables	<constructor>: creates a structure for the result of this mashup or for an intermediate variable. You define the nodes of the result and use mashup expressions to define the data from a variable to fill these nodes. <appendresult>: appends a structure of nodes to the result of this mashup or to an intermediate variable. This is typically used in repeating loops to handle results with repeated sections. You define the nodes of the structure to append and use mashup expressions to define the data from a variable to fill these nodes. <select>: creates a structure for the mashup result or for an intermediate variable with only selected nodes from a repeating set of items. See also <join> with a <select> child and <group>.
Controlling Mashup Processing Flow	<if>: handles if-elseif-else processing for a mashup script based on a condition defined in XPath 2.0. You can include any mashup statements in any section of <if>. <for>: processes a loop of any mashup statements based on a sequential count. <foreach>: processes a loop of any mashup statements either iterating sequentially through each node in a set of nodes from a variable or processing each loop concurrently. The set is an XPath 2.0 'sequence' defined by an expression. <while>: processes a loop of any mashup statements as long as a condition is true. The condition is defined in a XPath expression. <break>: explicitly stops processing the current loop and all subsequent loops in <for>, <foreach> or <while>. This can be used in <if>, <elseif> or <else> when they are used within looping statements. <parallel>: processes groups of mashup statements concurrently, as separate parallel flows. The groups of statements for each concurrent task are defined within <sequence> children, which can include variable declarations and any mashup statement. Database Mashable Transactions: using <presto:beginTransaction>, <presto:commitTransaction> and <presto:rollbackTransaction>. SQL Transactions: using <sqlBeginTransaction>, <sqlCommit> and <sqlRollback>.
Handling or Throwing Exceptions	<try>: to execute a block of EMML statements and catch and handle any exceptions from those statements. <throw>: to throw an exception for this mashup or macro. If this exception is not caught in a <catch> block in this mashup or macro, this also forceably stops mashup/macro processing. <return>: to forceably stop mashup or macro processing and return the current value of <output> as the mashup or macro result.
Defining and Using Custom Mashup Statements with Macros	<macro>: defines a custom EMML statement for use in mashups. Macros can contain any mashup statements. They accept input parameters and can return a result in an output variable. <macros>: root node for a macro library containing one or more macro definitions for use in any mashup hosted by a Presto Server. See also Creating and Registering Macros. Including Macro Domains in Mashup Scripts or Macros using <include>. Calling a Macro using the custom statement <macro:custom-macro-name> in a mashup script. See also Adding Custom Blocks to Presto Wires Using Macros.
Supporting Debugging	<display>: sends debugging messages to the log and console, optionally including the value of a variable or a portion of a variable. <assert>: defines assertions that are evaluated at runtime. Failures throw exceptions.
Adding Metadata to Mashups	<emml-meta> for metadata built into EMML <presto:macro-meta> for metadata for macros that are used as custom blocks in Wires or used solely in mashups written in EMML <presto:presto-meta> for metadata built into Presto <user-meta> for custom metadata to meet your requirements
Working with large datasets using RAQL	See Getting Started with Presto Analytics and RAQL Queries for more information on the EMML extensions you can use with large datasets and RAQL.