One major benefit of storing documents in WebDAV compared to simple file systems is that each document (and folder) also contains properties. Some properties are provided by the WebDAV system, others are user-defined, thereby allowing applications to add any information they wish to the WebDAV resources.
Properties are basically key value pairs, where the key is a qualified
name (QName) and the value is a string. Properties
are represented as XML elements, where the key is the name of the element and
the value is the content. This means that the restrictions of XML element names
and content apply to WebDAV properties.
A property with the name author in the
namespace http://myhost.com/nspace1 with the value
John could be represented as:
<ns1:author xmlns:ns1="http://myhost.com/nspace1">John</ns1:author>
WebDAV properties can also be XML fragments, where the content contains further XML elements.
The information in this document is organized under the following headings:
According to
RFC
2518, a live property is "a property whose semantics and
syntax are enforced by the server". Please refer to
RFC
2518,
RFC
3253, and
RFC
3744 for a list of the available live properties. All the
required live properties are supported by the Tamino. Some of
the optional live properties are not available. The live properties are
predefined and belong to the DAV:namespace.
An example of a live property is the content-type of a document, which
has the name
getcontenttype and
would be represented as:
<d:getcontenttype xmlns:d="DAV:">test/xml</d:getcontenttype>
According to
RFC
2518, a dead property is "a property whose semantics and
syntax are not enforced by the server. The server only records the value of a
dead property; the client is responsible for maintaining the consistency of the
syntax and semantics of a dead property". This basically means that dead
properties can be anything which can be represented as XML and which is not in
the DAV:namespace, since that namespace is reserved for the live
properties.
The Tamino Server offers some special properties which are used to control certain functional aspects. The special Tamino properties are in the namespace http://namespaces.softwareag.com/tamino/response2. These properties can only be applied to folders (WebDAV collections) and not to documents.
The property collection specifies the
Tamino collection to which the WebDAV folder is mapped. By default, a folder is
mapped to the collection ino:dav. If this property is set for a
WebDAV folder, all documents stored in this folder and all subfolders are
stored into the specified Tamino collection. Note that changing this property
does not move the documents stored in the WebDAV folder to the new collection;
only documents stored after the change are stored in the new Tamino collection.
Note also that the collection to which the mapping is set must exist before
specifying the mapping – it is not created automatically.
Since WebDAV is often used like a file system and should be able to store all kinds of documents, it is probably a good practice to set the mapped collections to optional schema usage, so that also documents without a matching schema can be stored to the respective WebDAV folder.
When a WebDAV folder is mapped to a Tamino collection, all non-XML data
is stored into the doctype ino:nonXML by default. If another
non-XML doctype should be used, it can be specified using the
non-xml-doctype property.
The Tamino Server provides a mechanism for putting WebDAV collections
under auto-version control. This means that any document stored into that
folder is automatically put under version control, and changes to the document
can lead to automatically generated versions. To activate this option, the
auto-version-control property can be set to any of
the four support auto-versioning modes: checkout-checkin,
checkout-unlocked-checkin, checkout, and locked-checkout. Set the value
off to deactivate this option after it has been
set.
In most cases, the WebDAV properties will probably be set by using a
WebDAV client or an application using a WebDAV API. When communicating directly
with the Tamino, the properties are set using the
PROPPATCH command. The following example uses
PROPPATCH to set to
mydoctype the doctype for non-XML documents stored
in the WebDAV folder myfolder:
PROPPATCH /tamino/mydb/ino:dav/ino:dav/myfolder HTTP/1.1
Host: mymachine.com
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
<?xml version="1.0" encoding="utf-8" ?>
<D:propertyupdate xmlns:D="DAV:"
xmlns:Z="http://www.w3.com/standards/z39.50/">
<D:set>
<D:prop>
<ino:non-xml-doctype
xmlns:ino="http://namespaces.softwareag.com/tamino/response2">
mydoctype
</ino:non-xml-doctype>
</D:prop>
</D:set>
</D:propertyupdate>
An example of a WebDAV client that supports the setting of properties and has been tested with Tamino is the DAV Explorer, an open source implementation from the University of California at Irvine (http://www.davexplorer.org/).
The properties that can be stored for one WebDAV resource are limited in size. About 32 kilobytes of space are available for each resource – depending on the type of encoding used, this can be considerably less than 32,000 characters. The property values are indexed using standard indexes, so performing searches on the properties should be very efficient.
The WebDAV properties are represented as XML fragments and can be accessed from within XQuery requests using special predefined functions. Please refer to the Tamino WebDAV Functions overview for details on these functions.