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Wednesday, February 6, 2008

A WebDAV Search Grammar for XML Properties

This version -00 Internet Draft specifies XS:xml-search, an optional
search grammar for use with the Web Distributed Authoring and
Versioning (WebDAV) SEARCH protocol. The full expression power of
XPath may exceed the requirement in simple use cases, therefore some
provisions are made in order to reduce the cost of implementing this
specification, as well as the computational cost of evaluating allowed
queries. The intent of the document is to extend the 'DAV:basicsearch'
grammar for dealing with properties whose values are XML fragments.
Since the WebDAV property namespace is flat, and resources may have at
most one value for a property of a given name, XML documents allowing
repeatable elements cannot be expressed as a set of independent WebDAV
properties (i.e by mapping some elements to properties), and the
'DAV:basicsearch' schema cannot be applied to such XML content because
it deals with property values as a whole. 'XS:xml-search' is proposed
as a different search grammar because it defines a new element
(namely XS:filter) that modify the query semantics. XML Extensibility:
The extensibility mechanism from Section 17 of RFC 4918 (i.e., to
process received XML documents as if unexpected elements and attributes,
and all children of unrecognized elements, were not present) may be
inappropriate when dealing with queries because they would not be
evaluated as specified by the client (e.g. the query criteria may be
loosen or the result record or may be incomplete). The omission of
unexpected content might not be realized by the client. The security
considerations of WebDAV SEARCH and WebDAV (RFC 4918), as well as
those of HTTP/1.1 and XML are applicable to the WebDAV extension
described in this document.

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