Internet DRAFT - draft-godoy-webdav-xmlsearch
draft-godoy-webdav-xmlsearch
Network Working Group R J. Godoy
Internet-Draft H. Minni
Intended status: Experimental Universidad Nacional del Litoral
Expires: August 28, 2008 February 25, 2008
A WebDAV Search Grammar for XML Properties
draft-godoy-webdav-xmlsearch-02
Status of This Memo
By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on August 28, 2008.
Copyright Notice
Copyright (C) The IETF Trust (2008).
Abstract
This document specifies xml-search, a search grammar for use with the
Web Distributed Authoring and Versioning (WebDAV) SEARCH protocol.
It extends the DAV:basicsearch grammar with XPath expressions that
are evaluated on resources' properties whose values are XML
fragments.
The full expression power of XPath may exceed the requirement in
simple use cases; therefore, some provisions are made in order to
Godoy & Minni Expires August 28, 2008 [Page 1]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
reduce the computational cost of evaluating allowed queries.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Notational conventions . . . . . . . . . . . . . . . . . . 4
1.2. Terms . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.4. WXS:xml-search and the PROPFIND response . . . . . . . . . 7
2. XPath . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1. Static and Dynamic Contexts . . . . . . . . . . . . . . . 8
2.2. Error and warnings . . . . . . . . . . . . . . . . . . . . 10
2.2.1. Warnings . . . . . . . . . . . . . . . . . . . . . . . 10
2.2.2. Errors (in SAP) . . . . . . . . . . . . . . . . . . . 11
2.2.3. Errors (in DEP) . . . . . . . . . . . . . . . . . . . 11
2.3. Numeric Predicates . . . . . . . . . . . . . . . . . . . . 12
3. Discovery of the Query Grammar . . . . . . . . . . . . . . . . 13
3.1. The DASL Response Header . . . . . . . . . . . . . . . . . 13
3.2. DAV:supported-query-grammar-set . . . . . . . . . . . . . 13
3.3. Discovery of the WXS:xml-search Query Schema . . . . . . . 14
4. The WXS:xml-search Grammar . . . . . . . . . . . . . . . . . . 15
4.1. Accepted Role Precondition . . . . . . . . . . . . . . . . 16
4.2. Selection . . . . . . . . . . . . . . . . . . . . . . . . 17
4.3. Query criteria . . . . . . . . . . . . . . . . . . . . . . 18
4.3.1. DAV:prop operand . . . . . . . . . . . . . . . . . . . 19
4.3.2. Literal Operands . . . . . . . . . . . . . . . . . . . 19
4.3.3. Relational operators . . . . . . . . . . . . . . . . . 19
4.3.4. The WXS:filter operator . . . . . . . . . . . . . . . 20
4.3.5. The WXS:is-well-formed operator . . . . . . . . . . . 20
4.4. Ordering . . . . . . . . . . . . . . . . . . . . . . . . . 20
4.5. SEARCH Status Codes for responses to WXS:xml-search
queries . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.6. Status Codes for Use in 'response' Elements . . . . . . . 22
4.7. Status Codes for Use in 'propstat' Elements . . . . . . . 22
4.8. Precondition and postcondition Codes . . . . . . . . . . . 22
4.8.1. WXS:property-must-be-well-formed-xml . . . . . . . . . 22
4.8.2. WXS:acceptable-role . . . . . . . . . . . . . . . . . 23
4.8.3. WXS:XPath-error . . . . . . . . . . . . . . . . . . . 23
4.8.4. DAV:search-scope-valid . . . . . . . . . . . . . . . . 23
4.8.5. WXS:known-literal-type . . . . . . . . . . . . . . . . 23
5. Query Schema for WXS:xml-search . . . . . . . . . . . . . . . 24
5.1. Property descriptions . . . . . . . . . . . . . . . . . . 24
5.2. Operator descriptions . . . . . . . . . . . . . . . . . . 25
5.2.1. WXS:opdesc-rule and WXS:operator . . . . . . . . . . . 26
5.2.2. WXS:repetition . . . . . . . . . . . . . . . . . . . . 27
5.2.3. WXS:alternative . . . . . . . . . . . . . . . . . . . 28
5.2.4. Implied operator description . . . . . . . . . . . . . 28
5.2.5. Extended operator description for
DAV:typed-literal Operand . . . . . . . . . . . . . . 29
Godoy & Minni Expires August 28, 2008 [Page 2]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
5.2.6. Description of DAV:like Operator . . . . . . . . . . . 30
5.3. Supporting Optional Functions . . . . . . . . . . . . . . 30
6. XML Extensibility . . . . . . . . . . . . . . . . . . . . . . 32
7. Security Considerations . . . . . . . . . . . . . . . . . . . 33
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 34
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 34
9.1. Normative References . . . . . . . . . . . . . . . . . . . 34
9.2. Informative References . . . . . . . . . . . . . . . . . . 36
Editorial Comments . . . . . . . . . . . . . . . . . . . . . . . .
Appendix A. Example WXS:xml-search query . . . . . . . . . . . . 39
Appendix B. Reported Issues . . . . . . . . . . . . . . . . . . . 40
B.1. Editorial Issues . . . . . . . . . . . . . . . . . . . . . 40
B.2. Technical Issues . . . . . . . . . . . . . . . . . . . . . 41
Appendix C. Change log (To be removed by RFC Editor before
publication) . . . . . . . . . . . . . . . . . . . . 42
C.1. changes in draft-godoy-webdav-xmlsearch-01 . . . . . . . . 42
C.2. changes in draft-godoy-webdav-xmlsearch-02 . . . . . . . . 42
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Note
Discussion about this draft should be addressed via
<www-webdav-dasl@w3.org>.
The latest version of this document can be accessed at
<http://purl.net/rjgodoy/webdav-xmlsearch-latest>.
Godoy & Minni Expires August 28, 2008 [Page 3]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
1. Introduction
This document specifies xml-search, an OPTIONAL search grammar for
use with the Web Distributed Authoring and Versioning (WebDAV) SEARCH
protocol. The search grammar defined by this document is a superset
of DAV:basicsearch [I-D.reschke-webdav-search].
The intent of this 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 (Section 9.1 of [RFC4918]),
XML documents allowing repeatable elements cannot be expressed as a
set of independent WebDAV properties (e.g., 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.
[note-intent]
WXS:xml-search is proposed as a different search grammar because it
defines a new element (namely WXS:filter) that modify the query
semantics. Had this been an extension of DAV:basicsearch, a server
would have ignored the WXS:filter elements (according to Section 17
of [RFC4918]) yielding results different from those requested by the
client. [note-RFC4918-sect17]
1.1. Notational conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
This specification defines elements in the
urn:ietf:params:xml:ns:webdav-xml-search XML namespace. (hereinafter
referred to as the "WXS namespace", though the prefix binding "WXS:"
is not normative). In natural language, an element like "xml-search"
in this namespace is sometimes referred to as "WXS:xml-search"
(without quotes). [note-namespace]
In element definitions, an element name prefixed with "WXS:" refers
to an element in the WXS namespace, and un-prefixed element names
refers to elements in the "DAV:" namespace.
The DTD fragments are normative up to extensibility rules defined in
Section 6. Unless noted otherwise, ordering of declared content is
not significative.
Note: when an error condition is described, it is said that "the
server MUST return" some indication of that error. Unless stated
otherwise, if several errors occur at the same time, any of them MAY
Godoy & Minni Expires August 28, 2008 [Page 4]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
be reported and any of them MAY be omitted as long as one of them is
reported.
1.2. Terms
This document uses the terms defined in [RFC2616], [RFC4918],
[W3C.REC-xpath20-20070123], and this section. Some definitions of
frequently used terms from [W3C.REC-xpath20-20070123] are
informatively included here.
Dynamic Context: (of an XPath expression) "the dynamic context of an
expression is defined as information that is available at the time
the expression is evaluated" (Section 2.1.2,
[W3C.REC-xpath20-20070123]).
Dynamic Evaluation Phase (DEP): "The dynamic evaluation phase is the
phase during which the value of an expression is computed. It occurs
after completion of the static analysis phase" (Section 2.3.3.2,
[W3C.REC-xpath20-20070123]).
Dynamic Error: "A dynamic error is an error that must be detected
during the dynamic evaluation phase and may be detected during the
static analysis phase. Numeric overflow is an example of a dynamic
error" (Section 2.3.1, [W3C.REC-xpath20-20070123]).
Implementation-defined: "indicates an aspect that MAY differ between
implementations, but MUST be specified by the implementor for each
particular implementation" (Section 1, [W3C.REC-xpath20-20070123]).
Implementation-dependent: "indicates an aspect that MAY differ
between implementations, is not specified by [this or any other]
specification, and is not required to be specified by the implementor
for any particular implementation" (Section 1,
[W3C.REC-xpath20-20070123]).
Role: a context within WXS:xml-search where the DAV:prop element is
expected. A role is "plain" if the DAV:prop element occurs as a
direct child of DAV:select, DAV:where, or DAV:order, and it is
"filtered" (also referred as XPath-enabled) if the DAV:prop element
occurs as a direct child of WXS:XPath.
Static Analysis Phase (SAP): "The static analysis phase depends on
the expression itself and on the static context. The static analysis
phase does not depend on input data (other than schemas)" (Section
2.3.3.1, [W3C.REC-xpath20-20070123]).
Static Context: (of an XPath expression) "the static context of an
expression is the information that is available during static
Godoy & Minni Expires August 28, 2008 [Page 5]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
analysis of the expression, prior to its evaluation" (Section 2.1.1,
[W3C.REC-xpath20-20070123]).
Static Error: "A static error is an error that MUST be detected
during the static analysis phase. A syntax error is an example of a
static error" (Section 2.3.1, [W3C.REC-xpath20-20070123]).
Type Error: "A type error may be raised during the static analysis
phase or the dynamic evaluation phase. During the static analysis
phase, a type error occurs when the static type of an expression does
not match the expected type of the context in which the expression
occurs. During the dynamic evaluation phase, a type error occurs
when the dynamic type of a value does not match the expected type of
the context in which the value occurs" (Section 2.3.1,
[W3C.REC-xpath20-20070123]).
1.3. Overview
Section 1.4 summarizes how this query grammar matches the PROPFIND
response, according to the requirement imposed by Section 2.3.2 of
[I-D.reschke-webdav-search].
Section 2 describes WXS:xml-search as an XPath host language, i.e., a
language where XPath expressions are embedded. This section
constrains some implementation-defined items from XPath. It also
includes design decisions in order to reduce the computational cost
of evaluating allowed queries.
Section 3 describes how this grammar is advertised, according to the
mechanisms for discovery of supported query grammars, defined in
Section 3 of [I-D.reschke-webdav-search]. This includes the Allow
and DASL headers in OPTIONS responses (Section 3.1), the DAV:
supported-query-grammar-set property (Section 3.2) and Query Schema
Discovery (Section 3.3 and Section 5).
Section 4 describes the grammar of a WXS:xml-search query. This
includes extending the specification of selection (Section 4.2) query
criteria (Section 4.3) and ordering (Section 4.4) with respect to
DAV:basicsearch. Additionally, some status (Section 4.5 to
Section 4.7) and precondition/postcondition codes (Section 4.8) are
defined.
Section 5 describes the Query Schema for advertising supported
features about properties (Section 5.1) and operators (Section 5.2),
and optional XPath functions available in a WXS:xml-search query
(Section 5.3).
Section 6 describes the specified behaviour when unexpected elements
Godoy & Minni Expires August 28, 2008 [Page 6]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
are found, providing a common ground for allowing clients that
implement arbitrary extensions to interoperate with other
implementations that does not include it.
1.4. WXS:xml-search and the PROPFIND response
A WXS:xml-search response contains a subset of the elements that a
PROPFIND response, listing the same properties on the same scope and
with the same depth, contains.
If a server supports specifying several scopes in a single query, and
these scopes exist, then the WXS:xml-search response will describe a
subset of the elements in several PROPFIND responses (one PROPFIND
for each scope).
The DAV:select element of a WXS:xml-search request defines the result
record. When either DAV:allprop or DAV:prop are used, both DAV:
select and PROPFIND define the same result set. Besides, a WXS:xml-
search request specifying not only DAV:allprop but also DAV:prop
defines the same result set as a PROPFIND specifying DAV:allprop and
DAV:include does.
WXS:xml-search introduce a new way for selecting properties: WXS:
filter, which "filters" elements from some property value according
to an XPath expression. If WXS:filter is used, the WXS:xml-search
response will contain a subset of elements from the filtered
property, while the PROPFIND response will contain the complete
value.
Queries may impose conditions about which or how many resources will
be included in the response, and servers may truncate the response at
their choice. Thus, a SEARCH response may not include some resources
from the specified scope, while all of them have to be included when
using PROPFIND.
Furthermore, WXS:xml-search defines additional preconditions and
postconditions codes that are not used with a PROPFIND response.
2. XPath
There are several items in XPath that are implementation-defined.
Some of them are defined in this section (as this protocol specifies
an XPath host language) while other are left to the criteria of the
implementors.
* Some components of the static and dynamic contexts are constrained
(Section 2.1).
Godoy & Minni Expires August 28, 2008 [Page 7]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
* A way for reporting errors and warnings is specified (Section 2.2).
* In some expressions, supporting numeric predicates is OPTIONAL
(Section 2.3).
* Implementations of this protocol MUST be based on the rules of
[W3C.REC-xml11-20060816] and [W3C.REC-xml-names11-20060816], and
apply them consistently.
* The self, child, descendant, descendant-or-self, parent and
attribute axes MUST be supported. An implementation MAY support
other axes, as described in the query schema. (This requirement is
aligned with the mandatory axes from [W3C.REC-xquery-20070123].)
* Support for the "Static Typing Feature" and "Static Typing
Extensions" (Appendix F.1 of [W3C.REC-xpath20-20070123]) is
implementation-defined.
2.1. Static and Dynamic Contexts
This specification defines REQUIRED values for some components of the
XPath static and dynamic context. Unless specified otherwise, the
constant values specified below MUST NOT be overwritten. Components
not listed here are "implementation-dependent".
Evaluation of an expression that relies on one or more "unassigned"
components raises the static error err:XPST0001 (if the component is
static) or the dynamic error err:XPDY0002 (if the component is
dynamic).
Definition of functions in the "Function signatures" set is given in
[W3C.REC-xpath-functions-20070123].
REQUIRED static values
+---------------------+---------------------------------------------+
| Component | Specified Value |
+---------------------+---------------------------------------------+
| XPath 1.0 | "false". |
| compatibility mode | |
| | |
| Statically known | All the namespace bindings in scope at the |
| namespaces | WXS:XPath element where the expression |
| | occurs plus ("fn:", |
| | "http://www.w3.org/2005/XPath-functions") |
| | unless overwritten. |
| | |
| Default | The default namespace of the WXS:XPath |
Godoy & Minni Expires August 28, 2008 [Page 8]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
| element/type | element where the expression occurs ("none" |
| namespace | if there is no default namespace). |
| | |
| Default function | "http://www.w3.org/2005/XPath-functions". |
| namespace | |
| | |
| Function signatures | fn:root($arg as node()?) as node()? |
| | fn:not($arg as item()*) as xs:boolean |
| | fn:count ($arg as item()*) as xs:integer |
| | fn:exists($arg as item()*) as xs:boolean |
| | fn:empty ($arg as item()*) as xs:boolean |
| | (may be overwritten). |
| | |
| Statically known | At least |
| collations | "http://www.iana.org/assignments/collation/ |
| | default" and applicable wildcard collations |
| | (Sections 3.1 and 3.2 of [RFC4790]). MAY |
| | be augmented with an implementation-defined |
| | set of collations. |
| | |
| Default collation | The collation matched by |
| | "http://www.iana.org/assignments/collation/ |
| | default" (the actual collation is |
| | implementation-defined) |
| | |
| Base URI | Unassigned. |
| | |
| Statically known | Initially unassigned. Overwriteable with |
| documents | an implementation-defined value. |
| | |
| Statically known | Initially unassigned. Overwriteable with |
| collections | an implementation-defined value. |
| | |
| Statically known | node()* |
| default collection | |
| type | |
+---------------------+---------------------------------------------+
REQUIRED dynamic values
+------------------+------------------------------------------------+
| Component | Specified Value |
+------------------+------------------------------------------------+
| Function | Implementation-defined, MUST be consistent |
| implementations | with function signatures. |
| | |
| Current dateTime | REQUIRED implementation-dependent value. |
| | |
Godoy & Minni Expires August 28, 2008 [Page 9]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
| Implicit | REQUIRED implementation-defined value. |
| timezone | |
| | |
| Available | Initially unassigned. Overwriteable with an |
| documents | implementation-defined value. |
| | |
| Available | Initially unassigned. Overwriteable with an |
| collections | implementation-defined value. |
| | |
| Default | Initially unassigned. Overwriteable with an |
| collection | implementation-defined value. |
+------------------+------------------------------------------------+
2.2. Error and warnings
This section describes the method for reporting XPath errors and
warnings. Error conditions are defined in
[W3C.REC-xpath20-20070123], and warning conditions are OPTIONAL and
implementation-defined.
For conformance with [W3C.REC-xpath20-20070123], implementations MAY
report any non-empty subset of errors. Additionally, if there is an
error (other than an XPath error) that causes the request to be
rejected, implementations MAY report the latter, with no mention to
the XPath errors.
The idref attributes of WXS:xpath-error and WXS:warning MAY be used
to refer to the id attribute of the WXS:xpath element whose content
raised the error or warning. The mechanism that implementations use
to return additional information is implementation-defined.
2.2.1. Warnings
The WXS:warning element contains at least one XML element, and MUST
NOT contain text or mixed content. Children of the WXS:warning
element represent warnings signaled during the analysis of the
expression.
<!ELEMENT WXS:warning ANY>
<!ATTLIST WXS:warning idref NAME #IMPLIED>
The DAV:multistatus and DAV:response elements, when used in response
to WXS:xml-search queries, are modified to include an OPTIONAL WXS:
warning element. Warnings raised during SAP apply to the whole query
and are reported within the WXS:warning element contained by DAV:
multistatus. Warnings raised during DEP only apply to a particular
resource and are reported within the DAV:response for that resource.
Godoy & Minni Expires August 28, 2008 [Page 10]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
<!ELEMENT multistatus (response*, responsedescription?,
WXS:warning?) >
<!ELEMENT response (href, ((href*, status)|(propstat+)),
error?, WXS:warning?,
responsedescription?, score?)
2.2.2. Errors (in SAP)
Any error (either a static, dynamic or type error) detected during
SAP invalidates the request. At this stage, errors are reported
through a WXS:xpath-error element included in a response whose root
element is DAV:error. The response status code is 400 (Bad Request).
<!ELEMENT WXS:xpath-error ANY>
<!ATTLIST WXS:xpath-error idref NAME #IMPLIED>
The WXS:xpath-error element MUST contain one or more elements
describing the error. For instance, if an err:XPST0003 were raised
(i.e. the XPath static error 0003: "a XPath expression is not a valid
instance of the grammar") the response would be:
HTTP/1.1 400 Bad Request
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
<error xmlns="DAV:">
<WXS:XPath-error
xmlns:WXS="urn:ietf:params:xml:ns:webdav-xml-search">
<err:XPST0003 xmlns:err="http://www.w3.org/2005/xqt-errors"/>
</WXS:XPath-error>
</error>
(Note: the use of the "err:" prefix follows the convention of
[W3C.REC-xpath20-20070123] but it is not normative.)
2.2.3. Errors (in DEP)
An expression may be statically valid and raise an error under some
dynamic conditions. Dynamic and type errors detected during DEP only
invalidates the expression which raises them, when evaluated with the
actual values of some resource property.
A server MAY ignore errors detected in DEP if:
-The error would occur within DAV:order, but that ordering
criteria is not evaluated (e.g., because other orders take
precedence, or because the query matches one or no resource).
-The error occurs within DAV:where part, and it does not affect
Godoy & Minni Expires August 28, 2008 [Page 11]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
the result. For instance, the error in (FALSE AND ERROR) may be
omitted because the result would have been FALSE anyway, and the
error in (TRUE OR ERROR) may be omitted because the result would have
been TRUE anyway.
If the error is not ignored, and the XPath expression was specified
within the DAV:select part, it MAY be reported in the DAV:propstat
element for the current property and resource. Otherwise, it MAY be
reported in the DAV:response element for the current resource. In
both cases the status code 409 (Conflict) MUST be used.
Although errors in DEP depend on the value of the property, an error
that is too frequent might have been caused by mistakes in the
client's request. Therefore, instead of returning a sequence of DAV:
response elements, all of which represent failures because of the
same error, a server MAY report an error in DEP as a general failure
invalidating the query itself, even if it is possible to evaluate
some resources or properties. [error-DEP]
When an error raised in DEP is reported as a general failure, the
response will be marshaled as in Section 2.2.2, but the response
status code MUST be 409 (Conflict) instead of 400 (Bad Request).
For instance, if err:XPTY0004 were raised during DEP ("the dynamic
type of a value does not match a required type"), the response would
be:
HTTP/1.1 409 Conflict
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
<error xmlns="DAV:">
<WXS:XPath-error
xmlns:WXS="urn:ietf:params:xml:ns:webdav-xml-search">
<err:XPTY0004 xmlns:err="http://www.w3.org/2005/xqt-errors"/>
</WXS:XPath-error>
</error>
the dynamic type of a value does not match a required type
2.3. Numeric Predicates
"A step is a part of a path expression that generates a sequence of
items and then filters the sequence by zero or more predicates"
(Section 3.2.1 of [W3C.REC-xpath20-20070123]). A step expression may
be either a FilterExpr or an AxisExpr.
"A predicate consists of an expression, called a predicate
Godoy & Minni Expires August 28, 2008 [Page 12]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
expression, enclosed in square brackets. A predicate serves to
filter a sequence, retaining some items and discarding others".
(Section 3.2.2 of [W3C.REC-xpath20-20070123])
Support for numeric predicates and other references to the context
position -e.g. by evaluating the fn:position() function- depends on
the sequence where the predicate applies.
Supporting numeric predicates in FilterExpr is OPTIONAL. If the step
expression is an AxisStep, the requirement level depends on the
specified axis. It is:
* NOT RECOMMENDED for the namespace and attribute axes, because the
relative order of elements within these axes is implementation-
dependent.
* Always REQUIRED for the parent, self, and ancestor axes.
* For the child, preceding-sibling, and following-sibling axes:
RECOMMENDED if the sequence order is semantically meaningful,
OPTIONAL otherwise.
* Always OPTIONAL for the descendant, descendant-or-self, ancestor-
or-self, preceding, and following axes.
[note-context-position]
The way this feature is supported when it is not REQUIRED is
implementation-dependent.
3. Discovery of the Query Grammar
If a resource supports the SEARCH method, then the server MUST list
SEARCH in the Allow header, as described in Section 3.1 of
[I-D.reschke-webdav-search].
3.1. The DASL Response Header
The DASL response header indicates server support for a query grammar
in the OPTIONS method. (Section 3.2 of [I-D.reschke-webdav-search])
The value of this header is a URI that indicates the type of grammar
supported. Servers MUST return the following header when the OPTIONS
method is invoked on any arbiter that supports the WXS:xml-search
grammar:
DASL:<urn:ietf:params:xml:ns:webdav-xml-search>
3.2. DAV:supported-query-grammar-set
The WebDAV property DAV:supported-query-grammar-set is REQUIRED for
any server supporting either [RFC3253] and/or [RFC3744] and
identifies the XML based query grammars that are supported by the
Godoy & Minni Expires August 28, 2008 [Page 13]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
search arbiter resource (Section 3.3 of [I-D.reschke-webdav-search]).
Servers implementing DAV:supported-query-grammar-set MUST report the
following grammar for each arbiter resource supporting WXS:xml-
search:
<DAV:grammar xmlns:DAV="DAV:">
<WXS:xml-search
xmlns:WXS="urn:ietf:params:xml:ns:webdav-xml-search"/>
</DAV:grammar>
3.3. Discovery of the WXS:xml-search Query Schema
Query Schema Discovery (QSD) is requested by means of the SEARCH
method, including an entity with a DAV:query-schema-discovery root
element. As specified in Section 4.1 of [I-D.reschke-webdav-search],
the response body takes the form of a DAV:multistatus element
(Section 13 of [RFC4918]), where DAV:response is extended to hold the
returned query grammar inside a DAV:query-schema container element.
If the DAV:query-schema-discovery element contains WXS:xml-search,
then the response marshaling MUST be performed as described in this
section and Section 5.
Since the supported query grammars may depend on the scope, the WXS:
xml-search element (when used for QSD) MAY contain a DAV:from
element. Other content is unexpected in this context.
If a request specifies several scopes, and the server supports them,
the response MUST only contain those descriptions that are common to
each scope.
Request:
SEARCH / HTTP/1.1
Host: host.example
Content-Type: application/xml
Content-Length: xxx
<query-schema-discovery xmlns="DAV:">
<WXS:xml-search
xmlns:WXS="urn:ietf:params:xml:ns:webdav-xml-search"/>
</query-schema-discovery>
Response:
HTTP/1.1 207 Multistatus
Content-Type: application/xml
Content-Length: xxx
Godoy & Minni Expires August 28, 2008 [Page 14]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
<multistatus xmlns="DAV:">
<response>
<href>http://host.example</href>
<status>HTTP/1.1 200 OK</status>
<query-schema>
<WXS:xml-search-schema
xmlns:WXS="urn:ietf:params:xml:ns:webdav-xml-search"/>
<!-- (See Section 5 for the actual contents) -->
</WXS:xml-search-schema>
</query-schema>
</response>
</multistatus>
4. The WXS:xml-search Grammar
The elements used in WXS:xml-search conform the semantics given in
[I-D.reschke-webdav-search] for the DAV:basicsearch grammar, and all
the operators defined in Section 5 of [I-D.reschke-webdav-search]
(i.e. %all_ops;) are valid in the context of a WXS:xml-search query.
Additionally, some elements in the "DAV:" namespace are allowed to
contain specific elements from the WXS:xml-search grammar.
Therefore, the semantics of a DAV:basicsearch valid query is
preserved when it is submitted as a WXS:xml-search query.
This grammar also allows the additional element WXS:filter, as well
as optional implementation-defined operators. The WXS:filter element
specifies an XPath expression (rooted on a single property, i.e. the
root element is the property whose name is included in the DAV:prop
element). It is both a query-operator and a special construct valid
within DAV:select and DAV:order elements.
<!-- "WXS:xml-search" element -->
<!ELEMENT WXS:xml-search (select?, from, where?, orderby?, limit?) >
<!-- "WXS:filter" and "WXS:xpath" -->
<!ELEMENT WXS:filter (prop, WXS:XPath)>
<!ELEMENT WXS:XPath #PCDATA >
<!ATTLIST WXS:xpath id ID #IMPLIED>
<!-- "DAV:select" element -->
<!ELEMENT select ( (allprop | prop | WXS:filter)+ )>
<!-- "DAV:where" element -->
<!ENTITY % wxs_ops "WXS:filter | WXS:is-well-formed" >
<!ELEMENT where ( %all_ops;|%wxs_ops;) >
Godoy & Minni Expires August 28, 2008 [Page 15]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
<!ELEMENT not ( %all_ops;|%wxs_ops; ) >
<!ELEMENT and ( (%all_ops;|%wxs_ops;)+ ) >
<!ELEMENT or ( (%all_ops;|%wxs_ops;)+ ) >
<!ELEMENT WXS:is-well-formed ( prop ) >
<!-- "DAV:order" element for WXS:xml-search-->
<!ELEMENT order ((prop | score | WXS:filter),
(ascending | descending)?)
4.1. Accepted Role Precondition
If the WXS:xml-search request includes a property with a role that is
not acceptable (e.g. the request specifies a filtered selection of a
property that is not XPath-enabled or it specifies ordering by a non-
sortable property), the server MUST reply with a 422 (Unprocessable
Entity) status code. The response's DAV:error element MUST contain
at least one WXS:acceptable-role preconditions (Section 4.8)
describing the failure for each rejected property.
If the request is not accepted because of a WXS:acceptable-role
precondition, the server SHOULD report all the failures, so that if
the client removes the conflicting properties then the modified query
will succeed this test.
If a property violates the preconditions for a role in both plain and
filtered forms, then the filtered form MAY be omitted in the error
response. (This rule does not apply for DAV:selectable since a
property may not be specified for both plain and filtered selection
in the same request).
Rejections because of several reasons (e.g. because a property is
neither DAV:searchable nor DAV:selectable) MAY be reported by means
of a single WXS:acceptable-role element. The DAV:prop element within
WXS:acceptable-role must contain a single property element.
If the server supports QSD, it MUST accept properties in the roles
described by the QSD response for the specified search scopes.
When a WXS:filter element refers to a live property that is known not
to be well-formed XML (because the server enforces other syntax), the
server SHOULD reject the request as described in this section,
instead of accepting the query and reporting a 409 (Conflict) for
each occurrence. (This implies that its QSD description SHOULD NOT
include any XPath-enabled role.)
Godoy & Minni Expires August 28, 2008 [Page 16]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
4.2. Selection
DAV:select defines the result record, which is a set of properties
and values (Section 5.3 of [I-D.reschke-webdav-search]). The allowed
children are DAV:allprop and DAV:prop (defined in Section 14 of
[RFC4918]) and WXS:filter (defined in this document).
If the DAV:select element is omitted, the successful response MUST
only contain the URIs of matched resources in one or more DAV:
response elements with status code 204 (No content). The response
root element is DAV:multistatus. If an error occurs, it MUST be
reported as described for the non-empty case.
The rest of this section describes the handling of non-empty DAV:
select elements
For each resource matching the query criteria and scope, the results
from all the WXS:filter selection-elements (i.e. all the WXS:filter
elements included within a DAV:select element) referred to the same
property MUST be returned into a single property of the DAV:response.
Because of filtering, the response is not required to be valid even
if the selected property contains an XML document that is valid
according to some DTD or XML schema.
For each resource matching the query criteria and scope, and for each
property selected through WXS:filter:
- When the actual property value does not contain a well-formed XML
fragment, a DAV:propstat with 409 (Conflict) code and postcondition
code WXS:property-must-be-well-formed-xml MUST be returned for that
resource and property (since the query semantics is not appropriate
for the actual property value).
- If the actual property value contains a well-formed XML fragment,
the matched elements are aggregated into the XML fragment for that
property and resource.
- If no elements are matched for that property and resource, it will
be reported as an empty element.
If a property does not exist, the server MUST either omit the
selected property from that resource record-set or return it within a
404 (Not Found) status code DAV:propstat.[note-OPTIONAL-404]
A client MUST NOT request both the plain property value and the
filtered one, since it is ambiguous (or, in the best case, redundant)
[note-select-prop-filter]. Hence, if DAV:select contains one or more
WXS:filter elements referring a property that is also selected via a
Godoy & Minni Expires August 28, 2008 [Page 17]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
plain DAV:prop element, the server MUST return a 400 (Bad Request)
response.
For instance, the following DAV:select element causes a 400 response:
<select xmlns="DAV:">
<filter>
<prop xmlns:A="http://a.example/"/>
<A:property/>
</prop>
<XPath>//foo</XPath>
</filter>
<prop xmlns:A="http://a.example/"/>
<A:property/>
</prop>
</select>
If DAV:allprop is specified, it is understood as in a PROPFIND
request [RFC4918]: (i.e., properties defined in RFC 4918, at a
minimum, plus dead properties MUST be returned). Hence, the set of
properties selected by allprop vary from resource to resource.
If the request includes not only DAV:allprop but also one or more
DAV:prop elements specifying properties that are already returned per
DAV:allprop, or the request includes a property twice in DAV:prop
elements, then the redundant properties MUST be ignored (i.e. a
single property value will be returned). This behaviour is similar
to that of the DAV:include element in a PROPFIND request (but DAV:
include is not defined for WXS:xml-search requests).
There is no error when a property that would be returned per DAV:
allprop is also specified within a WXS:filter element (since the
client may not be aware of the properties that will be returned when
DAV:allprop is specified). This combination MUST be addressed as
follows:
- Process the WXS:filter elements as usual. This result in
properties contained in DAV:propstat; elements with status code 200,
4xx, or 5xx, as appropriate.
- Select each property that would have been returned per DAV:
allprop in a PROPFIND request and was not included within a WXS:
filter element.
4.3. Query criteria
The DAV:where element specifies optional query criteria. Only those
resources that verify the query criteria are included in the result
set.
Godoy & Minni Expires August 28, 2008 [Page 18]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
4.3.1. DAV:prop operand
The result of the DAV:prop operand is the value of the specified
property of the resource being evaluated. If the property is a live
one, the result datatype SHOULD be the actual property datatype. If
the property is dead, or the server chooses to ignore the live
property datatype, the result MUST be of type xs:string.
Note: "A property name is a universally unique identifier that is
associated with a schema that provides information about the syntax
and semantics of the property" (Section 4.4 of [RFC4918]).
Therefore, each property name SHOULD be permanently associated with
at most one datatype.
4.3.2. Literal Operands
DAV:literal and DAV:typed-literal allow literal values to be placed
in an expression. Both literal are interpreted as defined in Section
5.10 and Section 5.11 of [I-D.reschke-webdav-search].
Besides, a request with a DAV:typed-literal specifying an unknown
type MUST be rejected by returning a response with status code 422
(Unprocessable Entity) and precondition code WXS:known-literal-type.
The xs:string type MUST NOT be unknown.
4.3.3. Relational operators
The relational operators take a property and literal operand. WXS:
xml-search inherits the five relational operators defined in
[I-D.reschke-webdav-search]: DAV:eq, DAV:lt, DAV:gt, DAV:lte and DAV:
gte.
For each property and pair of values being compared:
- per Section 4.2.1 of [W3C.REC-xmlschema-2-20041028] the result
of DAV:eq; is always defined, then DAV:eq; MUST NOT return NULL.
- all of DAV:lt, DAV:gt, DAV:lte and DAV:gte MUST be either
undefined or consistently defined. If they are defined, they MUST
also conform the result of DAV:eq (i.e., A == B iff A<=B and A>=B).
If the property type is known and it is a complex type, the result of
these operations SHOULD be undefined. [note-comparison-complex-type]
(Values within such properties may be compared by means of XPath
predicates.)
If the property type is known and it is a simple built-in ordered
type, the order relation used in the comparison SHOULD be that
defined in [W3C.REC-xmlschema-2-20041028].
Godoy & Minni Expires August 28, 2008 [Page 19]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
If the property type is known and it is a simple type, an
implementation-dependent order relation MAY be used. If a partial
order is used, then trying to compare two values that are not
comparable yields an undefined result.
In any case, the collation algorithm is implementation-dependent.
Other operators and operands retain the behaviours defined in
[I-D.reschke-webdav-search].
4.3.4. The WXS:filter operator
When used inside a DAV:where element (or a sub-element thereof) WXS:
filter evaluates as:
- TRUE if (and only if) the XPath expression matches at least one
element,
- FALSE if (and only if) no element within the property is
matched,
- NULL if (and only if) the property does not exist or its value
is not a well-formed XML fragment.
4.3.5. The WXS:is-well-formed operator
The WXS:is-well-formed operator takes a DAV:prop operand and returns:
- TRUE if (and only if) the property value is a well formed XML
fragment.
- FALSE if (and only if) the property value is not a well formed
XML fragment.
- NULL if (and only if) the property does not exist.
Supporting this operator is REQUIRED for properties that are WXS:
searchable, and OPTIONAL for properties that are only DAV:searchable.
4.4. Ordering
DAV:orderby specifies a lexicographical order on the result set to be
returned. Comparisons are applied as they occur in the DAV:orderby
element, earlier comparisons being more significant (Section 5.6 of
[I-D.reschke-webdav-search]).
When used within WXS:xml-search, a DAV:orderby element MUST contain
one or more DAV:order elements, which are allowed to contain a DAV:
prop, a DAV:score, or a WXS:filter elements.
When DAV:order contains a DAV:prop element, the ascending
(alternatively, descending) order MUST be consistent with the
comparison performed by DAV:lte (alternatively, DAV:gte):
- If A<=B (alternatively, A>=B) according to DAV:lte, then A collates
Godoy & Minni Expires August 28, 2008 [Page 20]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
before B.
- If A<=B (alternatively, A>=B) is undefined, then the collation
order is implementation-dependent.
When DAV:order contains a DAV:score element, an integer comparison is
performed on each DAV:score value computed for the DAV:contains
operation.
When DAV:order contains a WXS:filter element, result-sets will be
logically partitioned in three equivalence classes, based on the
evaluation of WXS:filter (as defined in Section 4.3). The
equivalence classes are totally ordered (in ascending order) as: NULL
< false < true.
Ordering within each equivalence class (i.e. ordering among all the
responses for which the WXS:filter element evaluates to the same
value) is implementation-dependent. (The order specified for the
item-type in the sequence returned by the xpath expression MAY be
used.)
4.5. SEARCH Status Codes for responses to WXS:xml-search queries
- 207 (Multistatus) The server accepted the request. The result
set are returned within a DAV:multistatus element.
- 400 (Bad Request) Error in SAP, or the query includes both a
plain DAV:prop and a WXS:filter specifying the same property name.
- 403 (Forbidden) The server rejected the request because the user
has no privileges for performing queries under the specified arbiter
resource.
- 404 (Not found) The arbiter resource does not exist.
- 409 (Conflict) Error in DEP (general failure) or invalid scope.
- 422 (Unprocessable Entity)
A property was specified in a role that is rejected for that
property.
An unknown type was specified in DAV:typed-literal.
A required extension is not supported.
Other status codes may be returned (redirections, client errors,
server errors), with the meaning defined in [RFC2616].
The 207 status code MUST be used if and only if a result set is
included in the response (an empty result set is allowed if the query
does not match any resource).
If the query could not be performed because of several errors, the
error that is reported is implementation-dependent.
If the client has no privileges for testing whether the arbiter
Godoy & Minni Expires August 28, 2008 [Page 21]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
exists then 403 (Forbidden) SHOULD be used instead of 404 (Not
found). If the client has no privileges for accessing the specified
scope then 409 (Conflict) MUST be returned
4.6. Status Codes for Use in 'response' Elements
- 204 (No Content) if the resource exists and no selection list
was specified (i.e. the DAV:select element is empty).
- 209 (Conflict) Error in DEP. The search was invalidated for
resources identified by DAV:href elements in the response.
If a selection list was specified, the response MUST NOT contain a
DAV:status element, but a DAV:propstat listing the selected
properties.
If the client has no privileges for testing whether a resource
exists, that resource MUST be silently omitted from the response.
5xx status codes MAY be used if an error occurs when accessing the
resource.
4.7. Status Codes for Use in 'propstat' Elements
- 200 (OK) for each selected property, if the property exists.
- 403 (Forbidden) if the client has no privileges for accessing
the selected property.
- 404 (Not Found) for each property selected through DAV:allprop,
DAV:prop or WXS:filter if the property does not exist (OPTIONAL).
- 409 (Conflict) if a property specified in a selection WXS:filter
element does not contains well-formed XML. The associated
postcondition MUST be WXS:property-must-be-well-formed-xml.
If the client has no privileges for testing whether the property
exists, the server SHOULD either omit the property or return a 404
(Not found) status code (instead of 403).
5xx status codes MAY be used if an error occurs when accessing the
property value.
4.8. Precondition and postcondition Codes
4.8.1. WXS:property-must-be-well-formed-xml
Type: postcondition
Use with: /multistatus/response/propstat/error, 409 Conflict
Purpose: the actual property value does not contain a well-formed XML
Godoy & Minni Expires August 28, 2008 [Page 22]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
fragment, and the property was specified in a WXS:filter element.
<!ELEMENT WXS:property-must-be-well-formed-xml EMPTY>
4.8.2. WXS:acceptable-role
Type: precondition
Use with: /error, 422 Unprocessable Entity
Purpose: the WXS:xml-search request includes a property for a role
where it is not acceptable.
<!ELEMENT WXS:acceptable-role (prop, searchable?,
selectable?, sortable?)>
4.8.3. WXS:XPath-error
Type: precondition/postcondition
Use with:
/error, 400 Bad Request (precondition)
/error, 409 Conflict (precondition)
/multistatus/response/error, 409 Conflict (postcondition)
/multistatus/response/propstat/error, 409 Conflict (postcondition)
Purpose: The query includes an XPath expression that raises an error.
(see Section 2.2.)
4.8.4. DAV:search-scope-valid
Type: precondition
Use with: /error, 409 Conflict
Defined in [I-D.reschke-webdav-search]
4.8.5. WXS:known-literal-type
Type: precondition
Use with: /error, 422 Unprocessable Entity
Purpose: The query includes a DAV:typed-literal that specifies an
unknown data-type. The data-type name is included into the element
Godoy & Minni Expires August 28, 2008 [Page 23]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
content.
<!ELEMENT WXS:known-literal-type #PCDATA>
5. Query Schema for WXS:xml-search
The query schema provides information about the set of available
properties and implemented operators.
The query schema is marshaled within a WXS:xml-search-schema element.
This element contains an unordered set of property descriptions (DAV:
propdesc), operator description rules (WXS:opdesc-rule) and supported
optional functions (WXS:function-set).
<!ELEMENT WXS:xml-search-schema (propdesc|WXS:opdesc-rule
|WXS:function-set)* ) >
5.1. Property descriptions
The semantics of DAV:propdesc, when used within a WXS:xml-search-
schema is extended for describing whether a property may be used as
root element of an XPath expression within a WXS:filter element.
Since WXS:filter may appear in three different places (the record-set
definition, the query criteria and the ordering criteria), the server
may allow or disallow it on a separate basis. If WXS:selectable,
WXS:searchable or WXS:sortable is present, then the server MUST allow
this property to be used within a WXS:filter element in the
applicable context (role)
<!ELEMENT propdesc (prop|any-other-property), datatype?,
(searchable | WXS:searchable)?,
(selectable | WXS:selectable)?,
(sortable | WXS:sortable?),
caseless?,
WXS:axis*, WXS:function-set* >
<!ELEMENT WXS:selectable EMPTY >
<!ELEMENT WXS:searchable EMPTY >
<!ELEMENT WXS:sortable EMPTY >
<!ELEMENT WXS:axis EMPTY>
<!ATTLIST WXS:axis name (namespace |
| ancestor | ancestor-or-self
Godoy & Minni Expires August 28, 2008 [Page 24]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
| following | following-sibling
| preceding | preceding-sibling) #REQUIRED>
Properties that are WXS:selectable or WXS:searchable are also DAV:
selectable or DAV:searchable respectively. For instance, if a
property may be selected through an XPath expression then it is
plainly selectable, and if a property may be used within a WXS:filter
query criterion then it may be used as an operand of DAV:is-defined,
DAV:is-well-formed.
Properties that are WXS:sortable are not DAV:sortable, because
comparison of complex types is undefined. Properties MUST NOT be
DAV:sortable and WXS:sortable at the same time.
The server MUST allow described properties to be used in the role for
which they were advertised. This hint does not assert whether the
property is defined on every resource in the scope, and does not
assert whether the property value is well-formed XML.
There SHOULD be one description for DAV:any-other-property. There
MUST NOT be more than one description for each property, and one
description for DAV:any-other-property.
The "name" attribute of the WXS:axis element specifies the name of an
optional axis, and the WXS:function-set element (Section 5.3)
specifies optional functions, which the server supports for the
property being described.
5.2. Operator descriptions
Operators are described in a way that borrows some elements from ABNF
[RFC4234] (namely repetitions and alternatives). This approach
allows a flexible and compact description of operators. [note-opdesc]
<!-- "allow-pcdata" attribute -->
<!ATTLIST WXS:opdesc-rule allow-pcdata (yes|no) #IMPLIED >
<!-- "WXS:operator" element -->
<!ELEMENT WXS:operator EMPTY >
<!ATTLIST WXS:operator name NAME #REQUIRED >
<!ATTLIST WXS:operator namespace CDATA
"urn:ietf:params:xml:ns:webdav-xml-search" >
<!-- terminal elements -->
<!ENTITY % WXS:terminal (operand-literal|
operand-typed-literal|
Godoy & Minni Expires August 28, 2008 [Page 25]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
operand-property|
WXS:operand-XPath|
WXS:operand-nested-op) >
<!ELEMENT WXS:operand-XPath EMPTY>
<!ELEMENT WXS:operand-nested-op EMPTY>
<!-- content model description-->
<!ELEMENT WXS:opdesc-rule (WXS:operator+,
(WXS:alternative|WXS:repetition|
%terminal;)*
)>
<!ELEMENT WXS:alternative (WXS:repetition|%terminal;)>
<!ELEMENT WXS:repetition (WXS:alternative|WXS:repetition|
%terminal;)* >
<!ATTLIST WXS:repetition atleast CDATA "0" >
<!ATTLIST WXS:repetition atmost CDATA "infinity" >
5.2.1. WXS:opdesc-rule and WXS:operator
WXS:operator references the name of an operator. Several operators
may be defined by the same WXS:opdesc-rule, and several WXS:opdesc-
rule may define incremental alternatives (that is, an initial rule
may match one or more alternatives, with later rule definitions
adding to the set of alternatives, as in the ABNF construction Rule1
=/ Rule2 defined in section 3.3 of [RFC4234]).
For instance,
<opdesc-rule>
<operator name="lt" namespace="DAV:"/>
<operator name="gt" namespace="DAV:"/>
<operand-property/>
<alternative>
<operand-literal/>
<operand-typed-literal/>
</alternative>
</opdesc-rule>
is equivalent to
<opdesc-rule>
<operator name="lt" namespace="DAV:"/>
<operand-property/>
<operand-literal/>
</opdesc-rule>
Godoy & Minni Expires August 28, 2008 [Page 26]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
<opdesc-rule>
<operator name="lt" namespace="DAV:"/>
<operand-property/>
<operand-typed-literal/>
</opdesc-rule>
<opdesc-rule>
<operator name="gt" namespace="DAV:"/>
<operand-property/>
<operand-literal/>
</opdesc-rule>
<opdesc-rule>
<operator name="gt" namespace="DAV:"/>
<operand-property/>
<operand-typed-literal/>
</opdesc-rule>
Mandatory operators SHOULD be omitted from the actual schema returned
by a server (since their grammar is implied). If an operator is
defined or enhanced by an extension of this protocol, the server MUST
return rules (i.e. one or more WXS:opdesc-rule elements) for them.
If the enhanced operator is a mandatory one, then the alternative
rule applies. Hence, if the response includes
<opdesc-rule>
<operator name="eq" namespace="DAV:"/>
<operand-property/>
<FOO:operand-bar xmlns:FOO="http://foo.example/"/>
</opdesc-rule>
it means that the DAV:eq operator accepts a pair of (property, foo:
bar) operands, as well as it accepts the above-defined (property,
literal) and (property, typed-literal) alternatives (from the
implicit grammar).
The order in which operands are described is significant, because the
ordering of operands within an expression is significant.
5.2.2. WXS:repetition
The semantics of element WXS:repetition is similar to the ABNF
Variable Repetition (e.g: *Rule) defined in Section 3.6 of [RFC4234].
The optional attributes "atleast" and "atmost" indicates minimum and
maximum allowed occurrences of the described content.
Default values are atleast="0" and atmost="infinity" so that <WXS:
Godoy & Minni Expires August 28, 2008 [Page 27]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
repetition> allows any number of occurrences, including zero; <WXS:
repetition atleast="1"> requires at least one, with no upper limit;
<WXS:repetition atleast="3" atmost="3"> allows exactly 3 and <WXS:
repetition atleast="1" atmost="2"> allows one or two.
5.2.3. WXS:alternative
The semantics of element WXS:alternative is similar to the ABNF
Alternatives (e.g: Rule1 / Rule2) defined in Section 3.2 of
[RFC4234].
For instance, <WXS:alternative> <WXS:operand-literal/> <WXS:operand-
typed-literal/> </WXS:alternative> will accept either an operand-
typed-literal or an operand-literal but not both.
5.2.4. Implied operator description
The following query schema describes the operators specified in this
document, as well as the operators from [I-D.reschke-webdav-search],
as they would be reported in a QSD response.
This description is implied, i.e. servers SHOULD NOT include it in
the response because these operators with these signatures are
mandatory.
<search-schema xmlns="DAV:"
<WXS:opdesc-rule>
<WXS:operator name="eq" namespace="DAV:"/>
<WXS:operator name="gt" namespace="DAV:"/>
<WXS:operator name="lt" namespace="DAV:"/>
<WXS:operator name="lte" namespace="DAV:"/>
<WXS:operator name="gte" namespace="DAV:"/>
<operand-property/>
<operand-literal/>
</WXS:opdesc-rule>
<WXS:opdesc-rule>
<WXS:operator name="not" namespace="DAV:"/>
<WXS:operand-nested-op/>
</WXS:opdesc-rule>
<WXS:opdesc-rule>
<WXS:operator name="and" namespace="DAV:"/>
<WXS:operator name="or" namespace="DAV:"/>
<WXS:repetition atleast="1">
<WXS:operand-nested-op/>
Godoy & Minni Expires August 28, 2008 [Page 28]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
</WXS:repetition>
</WXS:opdesc-rule>
<WXS:opdesc-rule>
<WXS:operator name="filter"/>
<operand-property/>
<WXS:operand-XPath/>
</WXS:opdesc-rule>
<WXS:opdesc-rule>
<WXS:operator name="is-defined" namespace="DAV:"/>
<WXS:operator name="is-well-formed"/>
<operand-property/>
</WXS:opdesc-rule>
<WXS:opdesc-rule>
<WXS:operator name="is-collection" namespace="DAV:"/>
</WXS:opdesc-rule>
</search-schema>
The DAV:is-collection operator is supported because WXS:xml-search
extends DAV:basicsearch grammar. It can be expressed by using WXS:
filter as:
<WXS:filter>
<prop><resourcetype/></prop>
<WXS:xpath>/collection</WXS:xpath>
</WXS:filter>
Tests for other resource types, as well as test for no resource type
may be expressed by the WXS:filter operator (provided that DAV:
resourcetype is WXS:searchable). For instance, testing whether a
resource has no resource type may be expressed as:
<WXS:filter>
<prop><resourcetype/></prop>
<WXS:xpath>count(/*)==0</WXS:xpath>
</WXS:filter>
5.2.5. Extended operator description for DAV:typed-literal Operand
The DAV:eq, DAV:gt, DAV:lt, DAV:lte, and DAV:gte operators MAY accept
a DAV:typed-literal operand, instead of DAV:literal. This
alternative is not implied (i.e. if supported, it MUST be included in
the QSD response). If DAV:typed-literal were supported (as defined
Godoy & Minni Expires August 28, 2008 [Page 29]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
in [I-D.reschke-webdav-search]), the QSD response would include the
following rule:
<WXS:opdesc-rule>
<WXS:operator name="eq" namespace="DAV:"/>
<WXS:operator name="gt" namespace="DAV:"/>
<WXS:operator name="lt" namespace="DAV:"/>
<WXS:operator name="lte" namespace="DAV:"/>
<WXS:operator name="gte" namespace="DAV:"/>
<operand-property/>
<operand-typed-literal/>
</WXS:opdesc-rule>
5.2.6. Description of DAV:like Operator
If the DAV:like operator is supported (as described in Section 5.2.2
of [I-D.reschke-webdav-search], the following rule MUST be included
in the QSD:
<WXS:opdesc-rule>
<WXS:operator name="like" namespace="DAV:"/>
<operand-property/>
<operand-literal/>
</WXS:opdesc-rule>
5.3. Supporting Optional Functions
Optional XPath functions supported by the server are described by
means of one or more WXS:function-set elements. The WXS:function-set
element may occur:
- As a child of WXS:xml-search-schema (with the "id" attribute
setted) defining a set of functions (WXS:function elements) that may
be referred from several properties.
- As a child of DAV:propdesc, with the "id" and "idref" attributes
implied, defining a set of functions (WXS:function elements) that is
specific for the property being described.
- As a child of DAV:propdesc, with the "idref" attribute pointing to
a "global" WXS:xml-search-schema element.
<!ELEMENT WXS:function-set (WXS:function*)>
<!ELEMENT WXS:function (WXS:function-param*,
Godoy & Minni Expires August 28, 2008 [Page 30]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
WXS:function-result?)>
<!ELEMENT WXS:function-param EMPTY >
<!ELEMENT WXS:function-result EMPTY >
<!ATTLIST WXS:function-set id ID #IMPLIED>
<!ATTLIST WXS:function-set idref IDREF #IMPLIED>
<!ATTLIST WXS:function name NMTOKEN #REQUIRED>
<!ATTLIST WXS:function-param type CDATA #REQUIRED
cardinality CDATA #IMPLIED
repeatable (true|false) false>
<!ATTLIST WXS:function-result type CDATA #REQUIRED
cardinality CDATA #IMPLIED>
>
Each WXS:function element contains zero or more WXS:function-param
elements, and zero or one WXS:function-result element, describing the
data type of function's parameters and result.
The "name" attribute of WXS:function represents the name of the
function being described.
The "type" attribute of WXS:function-param and WXS:function-result
specifies the data type of one function parameter, or the data type
of the function result, respectively.
The "cardinality" attribute is used for specifying the cardinality of
the sequence accepted as parameter or returned as a result. Its
allowed values are "?" (zero or one), "*" (zero or more) and "+" (one
or more), as specified in Section 1.4 of
[W3C.REC-xpath-functions-20070123].
The "repeatable" attribute is used for specifying whether a parameter
may be specified several times. It allows the values "true" and
"false", defaulting to "false" when not present. (Note:
cardinality="*" states that the actual parameter value may be a
sequence containing several instances of the specified type, thus it
is different from repeatable="true".)
Function name prefixes and type name prefixes are interpreted
according to the namespaces in scope. For this purpose, the item
type, the node types -e.g. node, element-
[W3C.REC-xpath-datamodel-20070123] and the pseudo-type "numeric" (a
shorthand for xs:integer, xs:decimal, xs:float and xs:double, defined
in Section 1.4 of [W3C.REC-xpath-functions-20070123]) are unprefixed,
and overrides any homonym name in the current default namespace.
Godoy & Minni Expires August 28, 2008 [Page 31]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
For instance, the following function-set describes: the two-
parameters version of fn:starts-with, the fn:concat function, and the
fn:trace function (defined in Section 4, 7.4.1 and 7.5.2 of
[W3C.REC-xpath-functions-20070123], respectively).
<WXS:function-set
xmlns:fn="http://www.w3.org/2005/XPath-functions"
xmlns:xs="http://www.w3.org/2001/XMLSchema">
<WXS:function name="fn:starts-with">
<WXS:function-param type="xs:string"/>
<WXS:function-param type="xs:string"/>
<WXS:function-result type="xs:boolean"/>
</WXS:function>
<WXS:function name="fn:concat">
<WXS:function-param type="xs:anyAtomicType"
repeatable="true"/>
<WXS:function-result type="xs:string"/>
</WXS:function>
<WXS:function name="fn:trace">
<WXS:function-param type="item" cardinality="*"/>
<WXS:function-param type="xs:string"/>
<WXS:function-result type="item" cardinality="*"/>
</WXS:function>
</WXS:function-set>
6. XML Extensibility
The extensibility mechanism from Section 17 of [RFC4918] (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 QSD response is the preferred method for advertising enhanced
capabilities for xml-search queries. Thus clients could assert
whether an extension is implemented by looking in the QSD beforehand.
Any extension of this grammar that modifies the query semantics (as
long as for yielding useless results if the extension were ignored)
SHOULD univocally identify itself by including one or more elements
in the QSD response. If the extension defines several conformance
Godoy & Minni Expires August 28, 2008 [Page 32]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
degrees, it should be clear from the QSD response which part of the
extension is actually implemented.
When an unexpected or unknown element is present in the request, the
server MUST:
- Ignore it (and its descendants), if the element is not a
descendant of DAV:where). The request is then processed as if the
element were not there.
- Fail with status code 422 (Unprocessable Entity) and
precondition code WXS:unexpected-operator, if the element is a
descendant of DAV:where).
The server MUST ignore all unexpected or unknown attributes which
occurs within expected elements.
<!ELEMENT WXS:unexpected-operator EMPTY>
7. Security Considerations
The security considerations of WebDAV SEARCH
[I-D.reschke-webdav-search], and WebDAV [RFC4918], as well as those
of HTTP/1.1 [RFC2616] and XML [RFC3023] are applicable to the WebDAV
extension described in this document.
The risk of denial of service attacks is greater than in the DAV:
basicsearch case, because evaluating some XPath expressions may be
computationally expensive. Implementors must be aware that many
valid (and required, even after subsetting optional XPath features)
expressions are computationally expensive to evaluate.
Implementations should deal with these expressions as a possible
denial of service attack (DOS), which may be committed either by
intention or by a good faith client submitting an overwhelming query.
Some examples of this queries include: visiting repeatedly the parent
and child axes, visiting several nodes with no apparent purpose (e.g.
a predicate that is evaluated on some other node, unrelated to the
focus), and requesting a result-set with redundant information (e.g.
nodes and information derived from those nodes by applying some
function).
There are no universally valid rules for determining whether an
expression is part of a DOS attack. Indeed, a server may accept an
expression that is deemed to be useful by the server implementors or
administrators, while other may reject it because of security
concerns. It may also accept or reject an expression because of
other variables, such as credentials presented by the user when
Godoy & Minni Expires August 28, 2008 [Page 33]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
authenticating (i.e. some users may be allowed to perform certain
kind of queries that would have been considered DOS if submitted by
other user).
For protecting from false negatives when detecting DOS, servers
should timeout when queries take too much time before completion.
8. IANA Considerations
This document defines XML elements in an XML namespace described by a
URN conforming the registry mechanism described in [RFC3688]. The
following URI assignment is requested
URI: urn:ietf:params:xml:ns:webdav-xml-search
Registrant Contact: See the "Author's Address" section of this
document.
XML: None. Namespace URIs do not represent an XML specification.
Reference: The last version of this document.
9. References
9.1. Normative References
[I-D.reschke-webdav-search] Reschke, J., "Web Distributed
Authoring and Versioning (WebDAV)
SEARCH",
draft-reschke-webdav-search-15
(work in progress),
February 2008.
[RFC2119] Bradner, S., "Key words for use
in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119,
March 1997.
[RFC2616] Fielding, R., Gettys, J., Mogul,
J., Frystyk, H., Masinter, L.,
Leach, P., and T. Berners-Lee,
"Hypertext Transfer Protocol --
HTTP/1.1", RFC 2616, June 1999.
[RFC3023] Murata, M., St. Laurent, S., and
D. Kohn, "XML Media Types",
RFC 3023, January 2001.
Godoy & Minni Expires August 28, 2008 [Page 34]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
[RFC3253] Clemm, G., Amsden, J., Ellison,
T., Kaler, C., and J. Whitehead,
"Versioning Extensions to WebDAV
(Web Distributed Authoring and Ve
rsioning)", RFC 3253, March 2002.
[RFC3688] Mealling, M., "The IETF XML
Registry", BCP 81, RFC 3688,
January 2004.
[RFC3744] Clemm, G., Reschke, J., Sedlar,
E., and J. Whitehead, "Web
Distributed Authoring and
Versioning (WebDAV)
Access Control Protocol",
RFC 3744, May 2004.
[RFC4790] Newman, C., Duerst, M., and A.
Gulbrandsen, "Internet
Application Protocol Collation
Registry", RFC 4790, March 2007.
[RFC4918] Dusseault, L., "HTTP Extensions
for Web Distributed Authoring and
Versioning (WebDAV)", RFC 4918,
June 2007.
[W3C.REC-xml-names11-20060816] Hollander, D., Layman, A., Tobin,
R., and T. Bray, "Namespaces in
XML 1.1 (Second Edition)", World
Wide Web Consortium Recommendatio
n REC-xml-names11-20060816,
August 2006, <http://www.w3.org/
TR/2006/
REC-xml-names11-20060816>.
[W3C.REC-xml11-20060816] Maler, E., Sperberg-McQueen, C.,
Cowan, J., Paoli, J., Bray, T.,
and F. Yergeau, "Extensible
Markup Language (XML) 1.1 (Second
Edition)", World Wide Web
Consortium Recommendation REC-
xml11-20060816, August 2006, <htt
p://www.w3.org/TR/2006/
REC-xml11-20060816>.
[W3C.REC-xmlschema-2-20041028] Malhotra, A. and P. Biron, "XML
Schema Part 2: Datatypes Second
Godoy & Minni Expires August 28, 2008 [Page 35]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
Edition", World Wide Web
Consortium Recommendation REC-
xmlschema-2-20041028,
October 2004, <http://www.w3.org/
TR/2004/
REC-xmlschema-2-20041028>.
[W3C.REC-xpath-datamodel-20070123] Fernandez, M., Malhotra, A.,
Nagy, M., Walsh, N., and J.
Marsh, "XQuery 1.0 and XPath 2.0
Data Model (XDM)", World Wide Web
Consortium Recommendation REC-
xpath-datamodel-20070123,
January 2007, <http://www.w3.org/
TR/2007/
REC-xpath-datamodel-20070123>.
[W3C.REC-xpath-functions-20070123] Walsh, N., Malhotra, A., and J.
Melton, "XQuery 1.0 and XPath 2.0
Functions and Operators", World
Wide Web Consortium Recommendatio
n REC-xpath-functions-20070123,
January 2007, <http://www.w3.org/
TR/2007/
REC-xpath-functions-20070123>.
[W3C.REC-xpath20-20070123] Berglund, A., Boag, S.,
Chamberlin, D., Kay, M., Robie,
J., Fernandez, M., and J. Simeon,
"XML Path Language (XPath) 2.0",
World Wide Web Consortium Recomme
ndation REC-xpath20-20070123,
January 2007, <http://www.w3.org/
TR/2007/REC-xpath20-20070123>.
9.2. Informative References
[RFC4234] Crocker, D., Ed. and P. Overell,
"Augmented BNF for Syntax
Specifications: ABNF", RFC 4234,
October 2005.
[W3C.REC-xquery-20070123] Boag, S., Robie, J., Chamberlin,
D., Fernandez, M., Florescu, D.,
and J. Simeon, "XQuery 1.0: An
XML Query Language", World Wide
Web Consortium Recommendation REC
-xquery-20070123, January 2007, <
Godoy & Minni Expires August 28, 2008 [Page 36]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
http://www.w3.org/TR/2007/
REC-xquery-20070123>.
Editorial Comments
[error-DEP] Besides, handling dynamic errors on a
separate basis imposes an additional
requirement, then supporting this
feature is left to the criteria of
implementors.
[note-comparison-complex-type] This seems to be a MUST in
[draft-reschke-webdav-search-14]
Section 5.5.4, but is relaxed here
since the property would be treated
as xs:string if the type were
ignored.
[note-context-position] When supporting numeric predicates
and context position references there
is a trade-off between expressive
power and implementation costs.
[note-intent] The authors' motivation for writing
this document is allowing metadata to
be searchable when presented as a
WebDAV property. Since it may be
encoded as specified by a third-party
schema, it should not be modified in
order to conform WebDAV.
[note-namespace] Since this protocol is experimental,
the authors do not suggest new
elements in order to not pollute the
"DAV:" namespace. Thus, an
experimental implementation of this
protocol will not conflict with the
following requirement from RFC 4918:
"(...) an XML element in the "DAV:"
namespace SHOULD NOT be used in the
request or response body unless that
XML element is explicitly defined in
an IETF RFC reviewed by a WebDAV
working group".
[note-opdesc] The operator description is only
intended for discovering whether the
server implements an extension
Godoy & Minni Expires August 28, 2008 [Page 37]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
operator. The DAV:operators element
from [I-D.reschke-webdav-search] is
not adopted here, because it cannot
describe the mandatory operators. On
the other hand, while XML Schemas
would have sufficed for this purpose,
this approach would have required
WXS:xml-search clients to be in
conformance to the XML Representation
of Schemas, which is much more than
necessary for achieving the above
mentioned goal (given that the
operators are not too complex). The
chosen approach is compared to ABNF,
in order to avoid further relation
with features that are available in
XML schemas but are unsupported for
xml-search-schema descriptions.
[note-OPTIONAL-404] The 404 status code for missing
properties is OPTIONAL in order to
avoid an extensive response if the
client selects several properties
that are seldom defined. Note this
behaviour is different from the
PROPFIND case, where the 404 status
code is REQUIRED for missing
properties (Section 9.1 of [RFC
4918], page 35).
[note-RFC4918-sect17] RFC4918: "(...) servers MUST process
received XML documents as if
unexpected elements and attributes
(and all children of unrecognized
elements) were not there"
[note-select-prop-filter] If the property value is not well-
formed XML specifying both DAV:prop
and WXS:filter is ambiguous because a
409 (Conflict) status code must be
returned per WXS:filter and the
complete property value must be
returned per DAV:prop. On the other
hand, if the property value were
well-formed XML, one of those
elements would have to be ignored.
Appendix A. Example WXS:xml-search query
Godoy & Minni Expires August 28, 2008 [Page 38]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
This example shows a request/response exchange for selecting the DAV:
getcontentlength property and the <M:title> and first <M:author>
elements of the <M:metadata> property, from resources that are
directly contained in the http://host.example.com/ collection, such
that the title (as described by an M:title element within the
M:metadata property) starts with letter "S". The first results will
have at least one M:author element present.
The response describes two resources:
- foo.pdf, with DAV:getcontentlength = 65536, author = "John Doe"
and title = "Sample Title"
- bar.txt, with DAV:getcontentlength = 1024, title = "Sample
Anonymous Resource" and no author.
Request:
SEARCH / HTTP/1.1
Host: host.example.com
Content-Type: application/xml
Content-Length: xxx
<searchrequest xmlns="DAV:">
<WXS:xml-search xmlns="DAV:"
xmlns:WXS="urn:ietf:params:xml:ns:webdav-xml-search"
xmlns:M ="http://example.org/metadata">
<select>
<WXS:filter>
<prop><M:metadata/></prop>
<WXS:xpath>/M:author[1]|/M:title</WXS:xpath>
</WXS:filter>
<prop><getcontentlength/></prop>
</select>
<from>
<scope>
<href>http://host.example.com/</href>
<depth>1<depth>
</scope>
</from>
<where>
<WXS:filter>
<prop><M:metadata/></prop>
<WXS:xpath>starts-with(/M:title,'S')</WXS:xpath>
</WXS:filter>
</where>
<orderby>
<order>
<WXS:filter>
<prop><M:metadata/></prop>
Godoy & Minni Expires August 28, 2008 [Page 39]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
<WXS:xpath>/M:author</WXS:xpath>
</WXS:filter>
<descending>
</order>
</orderby>
</WXS:xml-search>
</searchrequest>
Response:
HTTP/1.1 207 Multi-Status
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
<multistatus xmlns="DAV:"
xmlns:WXS="urn:ietf:params:xml:ns:webdav-xml-search"
xmlns:M ="http://example.org/metadata" >
<response>
<href>http://host.example.com/foo.pdf</href>
<propstat>
<prop>
<getcontentlength>65536</getcontentlength>
<M:metadata>
<M:author>John Doe</M:author>
<M:title>Sample title</M:title>
</M:metadata>
</prop>
<status>HTTP/1.1 200 OK<status>
</propstat>
</response>
<response>
<href>http://host.example.com/bar.txt</href>
<propstat>
<prop>
<getcontentlength>1024</getcontentlength>
<M:metadata>
<M:title>Sample Anonymous Resource</M:title>
</M:metadata>
</prop>
<status>HTTP/1.1 200 OK<status>
</propstat>
</response>
</multistatus>
Appendix B. Reported Issues
B.1. Editorial Issues
Godoy & Minni Expires August 28, 2008 [Page 40]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
Issue #E1, reported by Michael Kay on 2008-01-21.
http://lists.w3.org/Archives/Public/www-xpath-comments/2008JanMar/
0001.html, item (a).
http://lists.w3.org/Archives/Public/public-qt-comments/2008Jan/
0096.html, item (a).
Reference to XPath 2.0 Proposed Recommendation of 2006-11-21 should
be modified to refer Recommendation of 2007-01-23 2007. Suggest
avoid referring to a specifically dated version, so that readers are
referred to the latest edition at any given time, which may
incorporate errata.
Resolution: Refer XPath 2.0 Recommendation of 2007-01-23 (in turn, it
already suggests readers to check the latest version and errata).
Revisit this issue later with the RFC editor.
Issue #E2, reported by Michael Kay on 2008-01-21.
http://lists.w3.org/Archives/Public/www-xpath-comments/2008JanMar/
0001.html, item (c).
http://lists.w3.org/Archives/Public/public-qt-comments/2008Jan/
0096.html, item (c).
Since the namespace prefix "xs" is often used to refer to the XML
Schema namespace, it might be clearer to readers if a prefix other
than "XS" is used (perhaps "WXS"?).
Resolution: replace XS prefix with WXS.
B.2. Technical Issues
Issue #T1, reported by Michael Kay on 2008-01-21.
http://lists.w3.org/Archives/Public/www-xpath-comments/2008JanMar/
0001.html, item (e).
http://lists.w3.org/Archives/Public/public-qt-comments/2008Jan/
0096.html, item (e).
Suggest requiring the same subset of axes as XQuery chose.
Resolution: include descendant, descendant-or-self and parent as
REQUIRED axes (thus aligning with XQuery required axis). The
namespace axis is deprecated in XQuery, such deprecation is not
inherited by xmlsearch but the namespace axis is made OPTIONAL.
Issue #T2, reported by Michael Kay on 2008-01-21.
http://lists.w3.org/Archives/Public/www-xpath-comments/2008JanMar/
0001.html, item (f).
The minimum set of functions that an implementation must supply is
defined as being empty (no functions). There are some functions such
as not() and count() that would be absolutely indispensable.
Resolution: Include fn:not(item,item,...), fn:count(item,item,...),
fn:exists(item,item,...), fn:empty(item,item,...), fn:root(node). fn:
root(node) is supported because of the expansion for "/" and "//".
The default function namespace is set to "fn". The QSD is extended
for describing other functions that MAY be optionally supported.
Godoy & Minni Expires August 28, 2008 [Page 41]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
Appendix C. Change log (To be removed by RFC Editor before publication)
C.1. changes in draft-godoy-webdav-xmlsearch-01
- Include appendix B (reported issues) and C (change log).
- Removed typo about "DAV:xsl-search-schema", which does not exist.
- New issues in this version: #E1, #E2, #T1, #T2.
- Issues addressed in this version: #E1, #E2, #T1, #T2
- Some Security Considerations.
- Minor editorial changes.
C.2. changes in draft-godoy-webdav-xmlsearch-02
- Minor editorial changes.
- Updated reference to draft-reschke-webdav-search-15.
- Added allow-pcdata attribute in WXS:opdesc-rule, and modified
section about Literal Operands, per issues addressed in
draft-reschke-webdav-search-15 (discussion in http://lists.w3.org/
Archives/Public/www-webdav-dasl/2008JanMar/0022.html).
- Simplified the extension mechanism, because it was too complex to
be practical. Renamed precondition WXS:unexpected-content as WXS:
unexpected-operator.
Index
A
Attribute
allow-pcdata (WXS:opdesc-rule) 25
atleast (WXS:repetition) 25
atmost (WXS:repetition) 25
attrname (WXS:unexpected-content element) 33
cardinality (WXS:function-param) 30
cardinality (WXS:function-result) 30
id (WXS:function-set) 30
id (WXS:xpath) 15
idref (WXS:function-set) 30
idref (WXS:warning) 10
idref (WXS:xpath-error) 11
name (WXS:axis) 24
name (WXS:function) 30
Godoy & Minni Expires August 28, 2008 [Page 42]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
name (WXS:operator) 25
namespace (WXS:operator) 25
repeatable (WXS:function-param) 30
type (WXS:function-param) 30
type (WXS:function-result) 30
D
Dynamic Context 5
Dynamic Error 5
Dynamic Evaluation Phase (DEP) 5
E
Element
DAV:and 15
DAV:multistatus 11
DAV:not 15
DAV:or 15
DAV:order 15
DAV:propdesc 24
DAV:response 11
DAV:search-scope-valid 23
DAV:select 15
DAV:where 15
WXS:acceptable-role 23
WXS:alternative 25
WXS:axis 24
WXS:filter 15
WXS:function 30
WXS:function-param 30
WXS:function-result 30
WXS:function-set 30
WXS:is-well-formed 15
WXS:known-literal-type 23
WXS:opdesc-rule 25
WXS:operand-nested-op 25
WXS:operand-XPath 25
WXS:operator 25
WXS:property-must-be-well-formed-xml 22
WXS:repetition 25
WXS:searchable 24
WXS:selectable 24
WXS:sortable 24
WXS:unexpected-content 33
WXS:warning 10
WXS:xml-search 15
WXS:xml-search-schema 24
WXS:XPath 15
WXS:XPath-error 23
Godoy & Minni Expires August 28, 2008 [Page 43]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
WXS:xpath-error 11
Example
Bad Request, DAV:select 18
DASL Response Header 13
DAV:supported-query-grammar-set 14
Description of DAV:like Operator 30
Extended operator description for DAV:typed-literal operand 30
Implied operator description 28
QSD request 14
QSD response 14
WXS:function-set 32
WXS:opdesc-rule 26-27
WXS:XPath-error (in DEP) 12
WXS:XPath-error (in SAP) 11
xml-search request 39
xml-search response 40
I
Implementation-defined 5
Implementation-dependent 5
R
Role 5
S
Static Analysis Phase (SAP) 5
Static Context 5
Static Error 6
T
Type Error 6
Authors' Addresses
Roberto Javier Godoy
UNL - Facultad de Ingenieria y Ciencias Hidricas
Ciudad Universitaria, Ruta Nac. 168
S3001XAI Paraje "El Pozo"
Argentina
EMail: rjgodoy@fich.unl.edu.ar
URI: http://purl.oclc.org/NET/rjgodoy
Hugo Minni
UNL - Facultad de Ingenieria y Ciencias Hidricas
Ciudad Universitaria, Ruta Nac. 168
S3001XAI Paraje "El Pozo"
Godoy & Minni Expires August 28, 2008 [Page 44]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
Argentina
EMail: hminni@fich.unl.edu.ar
Godoy & Minni Expires August 28, 2008 [Page 45]
Internet-Draft WebDAV Search Grammar for XML Properties February 2008
Full Copyright Statement
Copyright (C) The IETF Trust (2008).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Intellectual Property
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
Acknowledgement
Funding for the RFC Editor function is provided by the IETF
Administrative Support Activity (IASA).
Godoy & Minni Expires August 28, 2008 [Page 46]
