WebDAV SEARCHgreenbytes GmbHSalzmannstrasse 152MuensterNW48159Germany+49 251 2807760+49 251 2807761julian.reschke@greenbytes.dehttp://www.greenbytes.de/tech/webdav/Oracle Corporation600 Oracle Parkway, M/S 6op3RedwoodshoresCA94065+1 650 506 5441Surendra.Reddy@oracle.comIntelligent Markets410 Jessie Street 6th floorSan FranciscoCA94103jrd3@alum.mit.eduFileNET Corp.3565 Harbor Blvd.Costa MesaCA92626+1 714 327 3403ababich@filenet.comWEBDAV DASL Working Group
This document specifies a set of methods, headers, and content-types composing
DASL, an application of the HTTP/1.1 protocol to efficiently search for DAV
resources based upon a set of client-supplied criteria.
Distribution of this document is unlimited. Please send comments to the
Distributed Authoring and Versioning (WebDAV) working group at
w3c-dist-auth@w3.org,
which may be joined by sending a message with subject
"subscribe" to w3c-dist-auth-request@w3.org.
Discussions of the WEBDAV working group are archived at URL:
http://lists.w3.org/Archives/Public/w3c-dist-auth/.
This document specifies a set of methods, headers, properties and content-types
composing WebDAV SEARCH, an application of the HTTP/1.1 protocol to efficiently search for DAV
resources based upon a set of client-supplied criteria.
Distribution of this document is unlimited. Please send comments to the
Distributed Authoring and Versioning (WebDAV) DASL working group at
www-webdav-dasl@w3.org,
which may be joined by sending a message with subject
"subscribe" to www-webdav-dasl-request@w3.org.
Discussions of the WEBDAV DASL working group are archived at URL:
http://www.w3.org/pub/WWW/Archives/Public/www-webdav-dasl/.
Need to rewrite introduction stating that is based on the expired WebDAV DASL internet draft.
This document defines WebDAV SEARCH, an application
of HTTP/1.1 forming a lightweight search protocol to transport queries
and result sets and allows clients to make use of server-side search facilities.
It is based on the expired draft for WebDAV DASL .
describes the motivation for DASL.
This document defines DAV Searching & Locating (DASL), an application
of HTTP/1.1 forming a lightweight search protocol to transport queries
and result sets and allows clients to make use of server-side search facilities.
describes the motivation for DASL.
DASL will minimize the complexity of clients so as to facilitate widespread
deployment of applications capable of utilizing the DASL search mechanisms.
DASL consists of:
the SEARCH method,the DASL response header,the DAV:searchrequest XML element,the DAV:queryschema property,the DAV:basicsearch XML element and query grammar, andthe DAV:basicsearchschema XML element.
For WebDAV-compliant servers, it also defines a new live property
DAV:supported-query-grammar-set.
DASL relies on the resource and property model defined by . DASL
does not alter this model. Instead, DASL allows clients to access DAV-modeled
resources through server-side search.
This draft uses the terms defined in , , and .
The augmented BNF used by this document to describe protocol elements is
exactly the same as the one described in Section 2.1 of . Because
this augmented BNF uses the basic production rules provided in Section
2.2 of , those rules apply to this document as well.
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 .
As this is an individual (non working group) submission, it should not use the DAV: namespace for any new elements. Need to collect feedback.
When an XML element type in the "DAV:" namespace is referenced in this document
outside of the context of an XML fragment, the string "DAV:" will be prefixed to
the element type.
Note that this draft currently defines elements and properties in the WebDAV namespace "DAV:",
which it shouldn't do as it isn't a work item of the WebDAV working group.
The reason for this is the desire for some kind of backward compatibility
to the expired DASL drafts and the
assumption that the draft may become an official RFC submission of the WebDAV working group
at a later point of time.
Similarily, when an XML element type in the namespace "http://www.w3.org/2001/XMLSchema"
is referenced in this document outside of the context of an XML fragment, the
string "xs:" will be prefixed to the element type.
One can express the basic usage of DASL in the following steps:
The client constructs a query using the DAV:basicsearch grammar.The client invokes the SEARCH method on a resource that will perform the
search (the search arbiter) and includes a text/xml or application/xml request entity that
contains the query.The search arbiter performs the query.The search arbiter sends the results of the query back to the client in
the response. The server MUST send an entitya text/xml entity that matches the
PROPFIND response.
The client invokes the SEARCH method to initiate a server-side search.
The body of the request defines the query. The server MUST emit
an entitytext/xml entity
matching the PROPFIND response.
The SEARCH method plays the role of transport mechanism for the query
and the result set. It does not define the semantics of the query. The
type of the query defines the semantics.
The client invokes the SEARCH method on the resource named by the Request-URI.
The Request-URI identifies the search arbiter.
Any HTTP resource may function as search arbiter. It is not a new type of
resource (in the sense of DAV:resourcetype as defined in ),
nor does it have to be a WebDAV-compliant resource.
This specification essentially defines a new type of Web resource,
of type "search arbiter". This raises a number of questions
regarding how this kind of resource interacts with existing HTTP
methods. I would expect to see a section which goes through and
details the interactions between HTTP and WebDAV methods and search
arbiters. For example, it seems reasonable to me to allow a search
arbiter to potentially reply to GET (perhaps with a human-meaningful
description of the capabilities of the arbiter), and for this GET
response to potentially be authorable using PUT, and locked using
LOCK. However, I wouldn't expect COPY, MOVE, or DELETE to work,
although I would expect PROPPATCH and PROPFIND to work OK. Another
issue is what kind of resource type a search arbiter returns in the
resourcetype property (I'd expect a <searcharbiter/> element).
How does a search arbiter respond to searches, if the search arbiter
URI is within a search scope? The answer to this is related to the
answer to whether a search arbiter has its own properties, body,
etc.
A SEARCH
arbiter is no special kind of resource and thus this spec doesn't define
any particular behaviour.
for my understanding the term "search arbiter" is an abstract term for a
piece of software, that suplies the SEARCH funcionality. As DASL is an
extension of WEBDAV, this piece of software will always be a complete WebDAV
server with the well defined behavior of GET, PROPFIND and so on. So no
additional definition is necessesary IMHO.
The SEARCH method defines no relationship between the arbiter and the
scope of the search, rather the particular query grammar used in the query
defines the relationship. For example, the FOO query grammar may force
the request-URI to correspond exactly to the search scope.
How does a DAV client discover which search arbiter can be used to
search a portion of the DAV namespace? At present, the
specification seems to imply two things (a) that "/" might be a
typical arbiter, and (b) that other arbiters can exist and you can
get redirected to them. If this issue isn't addressed in the
specification, it might lead to clients having hard-coded search
arbiter locations, thus forcing servers to put an arbiter at those
locations or be non-interoperable. Or, it will require clients to
be configured with the search arbiter location, which also seems
bad. It seems far better to have a predefined mechanism which
clients can use to discover the location of the search arbiter. One
simple mechanism would be to define a property on each collection
(but not each resource) which gives the location(s) of appropriate
arbiters.
If a WebDAV-enabled collection is smart enough to know about search arbiters
in scope, couldn't it be just forward SEARCH requests to those (making itself
a kind of proxy arbiter?). Issue closed as this doesn't seem to solve the
*general* discovery problem.
The server MUST process a text/xml or application/xml request body, and
MAY process request bodies in other formats. See for guidance
on packaging XML in requests.
If the client sends a text/xml or application/xml body, it MUST include
the DAV:searchrequest XML element. The DAV:searchrequest
XML element identifies the query grammar, defines the criteria, the result
record, and any other details needed to perform the search.
<!ELEMENT searchrequest ANY >
The DAV:searchrequest XML element contains a single XML element
that defines the query. The name of the query element defines the type
of the query. The value of that element defines the query itself.
Is the response from SEARCH cacheable? (No).
If the server returns 207 (Multistatus), then the search proceeded successfully
and the response MUST match that of a PROPFIND.
The results of this method SHOULD NOT be cached.
There MUST be one DAV:response for each resource that matched
the search criteria. For each such response, the DAV:href element
contains the URI of the resource, and the response MUST include a DAV:propstat
element.
In addition, the server MAY include DAV:response items in the
reply where the DAV:href element contains a URI that is not a
matching resource, e.g. that of a scope or the query arbiter. Each such
response item MUST NOT contain a DAV:propstat element, and MUST
contain a DAV:status
element (unless no property was selected). It SHOULD contain a DAV:responsedescription.
A response MAY include more information than PROPFIND defines so long as
the extra information does not invalidate the PROPFIND response. Query
grammars SHOULD define how the response matches the PROPFIND response.
This example demonstrates the request and response framework. The following
XML document shows a simple (hypothetical) natural language query.
The name of the query element is FOO:natural-language-query, thus the type
of the query is FOO:natural-language-query.
The name of the query element is natural-language-query in the XML namespace
"http://example.com/foo".
The actual query is "Find the
locations of good Thai restaurants in Los Angeles". For this hypothetical
query, the arbiter returns two properties for each selected resource.
Make sure that all examples specify an encoding when content type text/xml is used.
>> Request:SEARCH / HTTP/1.1
Host: ryu.com
Content-Type: application/xml
Content-Length: xxx
<?xml version="1.0" encoding="UTF-8"?>
<D:searchrequest xmlns:D="DAV:" xmlns:F="http://example.com/foo">
<F:natural-language-query>
Find the locations of good Thai restaurants in Los Angeles
</F:natural-language-query>
</D:searchrequest>
>> Response:HTTP/1.1 207 Multi-Status
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
<?xml version="1.0" encoding="UTF-8"?>
<D:multistatus xmlns:D="DAV:" xmlns:F="http://example.com/foo"
xmlns:R="http://ryu.com/propschema">
<D:response>
<D:href>http://siamiam.com/</D:href>
<D:propstat>
<D:prop>
<R:location>259 W. Hollywood</R:location>
<R:rating><R:stars>4</R:stars></R:rating>
</D:prop>
</D:propstat>
</D:response>
</D:multistatus>
>> Response:HTTP/1.1 207 Multi-Status
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
<?xml version="1.0" encoding="UTF-8"?>
<D:multistatus xmlns:D="DAV:" xmlns:R="http://ryu.com/propschema">
<D:response>
<D:href>http://siamiam.com/</D:href>
<D:propstat>
<D:prop>
<R:location>259 W. Hollywood</R:location>
<R:rating><R:stars>4</R:stars></R:rating>
</D:prop>
</D:propstat>
</D:response>
</D:multistatus>
A server MAY limit the number of resources in a reply, for example to limit
the amount of resources expended in processing a query. If it does so,
the reply MUST use status code 207, return a DAV:multistatus response
body and indicate a status of 507 (Insufficient Storage) for the search
arbiter URI. It SHOULD include the partial results.
When a result set is truncated, there may be many more resources that
satisfy the search criteria but that were not examined.
If partial results are included and the client requested an ordered
result set in the original request, then any partial results that are returned
MUST be ordered as the client directed.
Note that the partial results returned MAY be any subset of the result
set that would have satisfied the original query.
>> Request:SEARCH / HTTP/1.1
Host: gdr.com
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
... the query goes here ...
>> Response:
HTTP/1.1 207 Multistatus
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
<?xml version="1.0" encoding="utf-8"?>
<D:multistatus xmlns:D="DAV:">
<D:response>
<D:href>http://www.gdr.com/sounds/unbrokenchain.au</D:href>
<D:propstat>
<D:prop/>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
<D:response>
<D:href>http://tech.mit.edu/archive96/photos/Lesh1.jpg</D:href>
<D:propstat>
<D:prop/>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
<D:response>
<D:href>http://gdr.com</D:href>
<D:status>HTTP/1.1 507 Insufficient Storage</D:status>
<D:responsedescription xml:lang="en">
Only first two matching records were returned
</D:responsedescription>
</D:response>
</D:multistatus>
If an error occurred that prevented execution of the query, the server
MUST indicate the failure with the appropriate status code and SHOULD include
a DAV:multistatus element to point out errors associated with
scopes.
400 Bad Request. The query could not be executed. The request may be
malformed (not valid XML for example). Additionally, this can be used for
invalid scopes and search redirections.
422 Unprocessable entity. The query could not be executed. If a application/xml or text/xml
request entity was provided, then it may have been valid (well-formed)
but may have contained an unsupported or unimplemented query operator.
Section 2.5 states that the 507 (Insufficient Storage) status code
should be returned when SEARCH produces more responses that the
server is willing to immediately return. A 5xx status code isn't
appropriate for this case, since the response does have valid search
results, indicating that the client correctly submitted a search,
and this search was successfully performed by the server, even if it
isn't returning all search results. I recommend defining a new
status code for this case, 208 (Partial Results).
When results are truncated, server replies with a 507 and also returns an XML element.507 is currently in conflict with other specs. Need to avoid collisions.Use 207 (Multistatus) instead.507 (Insufficient Storage). The query produced more results than the
server was willing to transmit. Partial results have been transmitted.
The server MUST send a body that matches that for 207, except that there
MAY exist resources that matched the search criteria for which no corresponding
DAV:response exists in the reply.
A server MAY limit the number of resources in a reply, for example to limit
the amount of resources expended in processing a query. If it does so,
the reply MUST use status code 507. It SHOULD include the partial results.
When a result set is truncated, there may be many more resources that
satisfy the search criteria but that were not examined.
If partial results are included and the client requested an ordered
result set in the original request, then any partial results that are returned
MUST be ordered as the client directed.
Note that the partial results returned MAY be any subset of the result
set that would have satisfied the original query.
>> Request:SEARCH / HTTP/1.1
Host: gdr.com
Content-Type: application/xml
Content-Length: xxxxx
<?xml version="1.0" encoding="UTF-8"?>
<D:searchrequest xmlns:D="DAV:">
<D:basicsearch>
... the query goes here ...
</D:basicsearch>
</D:searchrequest>
>> Response:
HTTP/1.1 507 Insufficient Storage
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
<?xml version="1.0" encoding="UTF-8"?>
<D:multistatus xmlns:D="DAV:">
<D:response>
<D:href>http://www.gdr.com/sounds/unbrokenchain.au</D:href>
<D:propstat>
<D:prop/>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
<D:response>
<D:href>http://tech.mit.edu/archive96/photos/Lesh1.jpg</D:href>
<D:propstat>
<D:prop/>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
<D:response>
<D:href>http://gdr.com</D:href>
<D:status>HTTP/1.1 507 Insufficient Storage</D:status>
<D:responsedescription>
Only first two matching records were returned
</D:responsedescription>
</D:response>
</D:multistatus>
A client may submit a scope that the arbiter may be unable to query. The
inability to query may be due to network failure, administrative policy,
security, etc. This raises the condition described as an "invalid scope".
To indicate an invalid scope, the server MUST respond with a 400 (Bad
Request).
The response includes a text/xml body with a DAV:multistatus
element. Each DAV:response in the DAV:multistatus identifies
a scope. To indicate that this scope is the source of the error, the server
MUST include the DAV:scopeerror element.
>> Response:HTTP/1.1 400 Bad-Request
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
<?xml version="1.0" encoding="UTF-8"?>
<d:multistatus xmlns:d="DAV:">
<d:response>
<d:href>http://www.foo.com/X</d:href>
<d:status>HTTP/1.1 404 Object Not Found</d:status>
<d:scopeerror/>
</d:response>
</d:multistatus>
Servers MUST support discovery of the query grammars supported by a search
arbiter resource.
Clients can determine which query grammars are supported by an arbiter
by invoking OPTIONS on the search arbiter. If the resource supports SEARCH,
then the DASL response header will appear in the response. The DASL response
header lists the supported grammars.
Servers supporting the WebDAV extensions and/or
MUST also
report SEARCH in the live property DAV:supported-method-set for all search arbiter resources andsupport the live property DAV:supported-query-grammar-set as defined in .
The OPTIONS method allows the client to discover if a resource supports
the SEARCH method and to determine the list of search grammars supported
for that resource.
The client issues the OPTIONS method against a resource named by the
Request-URI. This is a normal invocation of OPTIONS defined in .
If a resource supports the SEARCH method, then the server MUST list
SEARCH in the OPTIONS response as defined by .
DASL servers MUST include the DASL header in the OPTIONS response. This
header identifies the search grammars supported by that resource.
>> Response:DASLHeader = "DASL" ":" Coded-URL-List
Coded-URL-List : Coded-URL [ "," Coded-URL-List ]
Coded-URL ; defined in section 9.4 of [RFC2518]
Here, a grammar is represented as an URI. Later, a grammar is identified by a Qualified XML name (URI reference + local name). This means that the client needs to be aware of a mapping from a URI (that's reported here) to an XML element name (that it can use in a query). Proposal: report XML-based grammars through a different mechanism in SEARCH (details to be done).
The DASL response header indicates server support for a query grammar in
the OPTIONS method. The value is a URI that indicates the type of grammar.
Note that although the URI can be used to identify each supported search
grammar, there is not necessarily a direct relationship between the URI and the
XML element name that can be used in XML based SEARCH requests (the element
name itself is identified by it's namespace name (a URI reference) and
the element's local name).
This header MAY be repeated.
For example:DASL: <http://foo.bar.com/syntax1>
DASL: <http://akuma.com/syntax2>
DASL: <DAV:basicsearch>
DASL: <http://example.com/foo/natural-language-query>
This WebDAV property is required for any server supporting either
and/or and
identifies the XML based query grammars that are supported by the search arbiter resource.
<!ELEMENT supported-query-grammar-set (supported-query-grammar*)>
<!ELEMENT supported-query-grammar grammar>
<!ELEMENT grammar ANY>
ANY value: a query grammar element type
This example shows that the server supports search on the /somefolder
resource with the query grammars: DAV:basicsearch, http://foo.bar.com/syntax1
and http://akuma.com/syntax2. Note that every server MUST support
DAV:basicsearch.
>> Request:OPTIONS /somefolder HTTP/1.1
Host: ryu.com
>> Response:HTTP/1.1 200 OK
Date: Tue, 20 Jan 1998 20:52:29 GMT
Allow: OPTIONS, GET, HEAD, POST, PUT, DELETE, TRACE, COPY, MOVE,
MKCOL, PROPFIND, PROPPATCH, LOCK, UNLOCK, SEARCH
DASL: <DAV:basicsearch>
DASL: <http://foo.bar.com/syntax1>
DASL: <http://akuma.com/syntax2>
This example shows the equivalent taking advantage of a server's support for
DAV:supported-method-set and DAV:supported-query-grammar-set.
>> Request:PROPFIND /somefolder HTTP/1.1
Host: ryu.com
Depth: 0
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
<?xml version="1.0" encoding="UTF-8" ?>
<propfind xmlns="DAV:">
<prop>
<supported-query-grammar-set/>
<supported-method-set/>
</prop>
</propfind>
>> Response:HTTP/1.1 207 Multi-Status
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
<?xml version="1.0" encoding="utf-8" ?>
<multistatus xmlns="DAV:">
<response>
<href>http://ryu.com/somefolder</href>
<propstat>
<prop>
<supported-query-grammar-set>
<supported-query-grammar>
<grammar><basicsearch/></grammar>
</supported-query-grammar>
<supported-query-grammar>
<grammar><syntax1 xmlns="http://foo.bar.com" /></grammar>
</supported-query-grammar>
<supported-query-grammar>
<grammar><syntax2 xmlns="http://akuma.com/"/></grammar>
</supported-query-grammar>
</supported-query-grammar-set>
<supported-method-set>
<supported-method name="COPY" />
<supported-method name="DELETE" />
<supported-method name="GET" />
<supported-method name="HEAD" />
<supported-method name="LOCK" />
<supported-method name="MKCOL" />
<supported-method name="MOVE" />
<supported-method name="OPTIONS" />
<supported-method name="POST" />
<supported-method name="PROPFIND" />
<supported-method name="PROPPATCH" />
<supported-method name="PUT" />
<supported-method name="SEARCH" />
<supported-method name="TRACE" />
<supported-method name="UNLOCK" />
</supported-method-set>
</prop>
<status>HTTP/1.1 200 OK</status>
</propstat>
</response>
</multistatus>
Note that the query grammar element names marshalled as part of the
DAV:supported-query-grammar-set can be directly used as element names in
an XML based query.
Servers MAY support the discovery of the schema for a query grammar.
The DASL response header provides means for clients to discover the
set of query grammars supported by a resource. This alone is not sufficient
information for a client to generate a query. For example, the DAV:basicsearch
grammar defines a set of queries consisting of a set of operators applied
to a set of properties and values, but the grammar itself does not specify
which properties may be used in the query. QSD for the DAV:basicsearch
grammar allows a client to discover the set of properties that are searchable,
selectable, and sortable. Moreover, although the DAV:basicsearch
grammar defines a minimal set of operators, it is possible that a resource
might support additional operators in a query. For example, a resource
might support a optional operator that can be used to express content-based
queries in a proprietary syntax. QSD allows a client to discover these
operators and their syntax. The set of discoverable quantities will differ
from grammar to grammar, but each grammar can define a means for a client
to discover what can be discovered.
In general, the schema for a given query grammar depends on both the
resource (the arbiter) and the scope. A given resource might have access
to one set of properties for one potential scope, and another set for a
different scope. For example, consider a server able to search two distinct
collections, one holding cooking recipes, the other design documents for
nuclear weapons. While both collections might support properties such as
author, title, and date, the first might also define properties such as
calories and preparation time, while the second defined properties such
as yield and applicable patents. Two distinct arbiters indexing the same
collection might also have access to different properties. For example,
the recipe collection mentioned above might also indexed by a value-added
server that also stored the names of chefs who had tested the recipe. Note
also that the available query schema might also depend on other factors,
such as the identity of the principal conducting the search, but these
factors are not exposed in this protocol.
It would be nice to avoid the definition of a "pseudo" property just for this special use case.
Each query grammar supported by DASL defines its own syntax for expressing
the possible query schema. A client retrieves the schema for a given query
grammar on an arbiter resource with a given scope by invoking the SEARCH
method on that arbiter, with that grammar and scope, with a query whose
DAV:select
element includes the DAV:queryschema property. This property is
defined only in the context of such a search, a server SHOULD not treat
it as defined in the context of a PROPFIND on the scope. The content of
this property is an XML element whose name and syntax depend upon the grammar,
and whose value may (and likely will) vary depending upon the grammar,
arbiter, and scope.
The query schema for DAV:basicsearch is defined in .
<!ELEMENT queryschema ANY >
In this example, the arbiter is recipes.com, the grammar is DAV:basicsearch,
the scope is also recipes.com.
>> Request:DAV:queryschema does not appear in a DAV:prop. Intentional?SEARCH / HTTP/1.1
Host: recipes.com
Content-Type: application/xml
Content-Length: xxx
<?xml version="1.0"?>
<D:searchrequest xmlns:D="DAV:" >
<D:basicsearch>
<D:select>
<D:queryschema/>
</D:select>
<D:from>
<D:scope>
<D:href>http://recipes.com</D:href>
</D:scope>
</D:from>
</D:basicsearch>
</D:searchrequest>
>> Request:SEARCH / HTTP/1.1
Host: recipes.com
Content-Type: application/xml
Content-Length: xxx
<?xml version="1.0"?>
<searchrequest xmlns="DAV:">
<basicsearch>
<select>
<prop>
<queryschema/>
</prop>
</select>
<from>
<scope>
<href>http://recipes.com</href>
</scope>
</from>
</basicsearch>
</searchrequest>
>> Request:DAV:queryschema was selected, but DAV:querygrammar was returned.HTTP/1.1 207 Multistatus
Content-Type: application/xml
Content-Length: xxx
<?xml version="1.0"?>
<D:multistatus xmlns:D="DAV:">
<D:response>
<D:href>http://recipes.com</D:href>
<D:propstat>
<D:prop>
<D:querygrammar>
<D:basicsearchschema>
/See section 5.19.9 for actual contents)
</D:basicsearchschema>
</D:querygrammar>
</D:prop>
<D:status>HTTP/1.1 200 Okay</D:status>
</D:propstat>
</D:response>
</D:multistatus>
>> Response:HTTP/1.1 207 Multistatus
Content-Type: application/xml
Content-Length: xxx
<?xml version="1.0"?>
<multistatus xmlns="DAV:">
<response>
<href>http://recipes.com</href>
<propstat>
<prop>
<queryschema>
<basicsearchschema>
(See section "Query schema for DAV:basicsearch" for
the actual contents)
</basicsearchschema>
</queryschema>
</prop>
<status>HTTP/1.1 200 OK</status>
</propstat>
</response>
</multistatus>
DAV:basicsearch uses an extensible XML syntax that allows clients
to express search requests that are generally useful for WebDAV scenarios.
DASL-extended servers MUST accept this grammar, and MAY accept others grammars.
DAV:basicsearch has several components:DAV:select provides the result record definition.DAV:from defines the scope.DAV:where defines the criteria.DAV:orderby defines the sort order of the result set.DAV:limit provides constraints on the query as a whole.Where does xml:lang go in a query?What would be the *purpose* of putting xml:lang into a query?Searches on XML chunks
that include namespaces. Need to expand out the XML namespace when doing the
search (i.e., do search on DAV:foo, not X:foo xmlns:X="DAV:") Also an issue
for expressing searches on XML sub-elements of properties.
I think this is out-of-scope for now.
<!ELEMENT basicsearch (select, from, where?, orderby?, limit?) >
<!ELEMENT select (allprop | prop) >
<!ELEMENT from (scope) >
<!ELEMENT scope (href, depth?) >
<!ENTITY %comp_ops "eq | lt | gt| lte | gte">
<!ENTITY %log_ops "and | or | not">
<!ENTITY %special_ops "isdefined">
<!ENTITY %string_ops "like">
<!ENTITY %content_ops "contains">
<!ENTITY %all_ops "%comp_ops; | %log_ops; | %special_ops; |
%string_ops; | %content_ops;">
<!ELEMENT where ( %all_ops; ) >
<!ELEMENT and ( ( %all_ops; ) +) >
<!ELEMENT or ( ( %all_ops; ) +) >
<!ELEMENT not ( %all_ops; ) >
<!ELEMENT lt ( prop , literal ) >
<!ATTLIST lt casesensitive (1|0) "1" >
<!ELEMENT lte ( prop , literal ) >
<!ATTLIST lte casesensitive (1|0) "1" >
<!ELEMENT gt ( prop , literal) >
<!ATTLIST gt casesensitive (1|0) "1" >
<!ELEMENT gte ( prop , literal ) >
<!ATTLIST gte casesensitive (1|0) "1" >
<!ELEMENT eq ( prop , literal ) >
<!ATTLIST eq casesensitive (1|0) "1" >
<!ELEMENT literal (#PCDATA)>
<!ATTLIST literal xml:space (default|preserve) preserve >
<!ELEMENT isdefined (prop) >
<!ELEMENT like (prop, literal) >
<!ATTLIST like casesensitive (1|0) "1" >
<!ELEMENT contains (#PCDATA)>
<!ELEMENT orderby (order+) >
<!ELEMENT order (prop, (ascending | descending)?)
<!ATTLIST order casesensitive (1|0) "1" >
<!ELEMENT ascending EMPTY>
<!ELEMENT descending EMPTY>
<!ELEMENT limit (nresults) >
<!ELEMENT nresults (#PCDATA) >
<!ELEMENT basicsearch (select, from, where?, orderby?, limit?) >
<!ELEMENT select (allprop | prop) >
<!ELEMENT from (scope) >
<!ELEMENT scope (href, depth) >
<!ENTITY %comp_ops "eq | lt | gt| lte | gte">
<!ENTITY %log_ops "and | or | not">
<!ENTITY %special_ops "is-collection | isdefined">
<!ENTITY %string_ops "like">
<!ENTITY %content_ops "contains">
<!ENTITY %all_ops "%comp_ops; | %log_ops; | %special_ops; |
%string_ops; | %content_ops;">
<!ELEMENT where ( %all_ops; ) >
<!ELEMENT and ( ( %all_ops; ) +) >
<!ELEMENT or ( ( %all_ops; ) +) >
<!ELEMENT not ( %all_ops; ) >
<!ELEMENT lt ( prop , literal ) >
<!ATTLIST lt casesensitive (1|0) "1" >
<!ELEMENT lte ( prop , literal ) >
<!ATTLIST lte casesensitive (1|0) "1" >
<!ELEMENT gt ( prop , literal) >
<!ATTLIST gt casesensitive (1|0) "1" >
<!ELEMENT gte ( prop , literal ) >
<!ATTLIST gte casesensitive (1|0) "1" >
<!ELEMENT eq ( prop , literal ) >
<!ATTLIST eq casesensitive (1|0) "1" >
<!ELEMENT literal (#PCDATA)>
<!ELEMENT isdefined (prop) >
<!ELEMENT like (prop, literal) >
<!ATTLIST like casesensitive (1|0) "1" >
<!ELEMENT contains (#PCDATA)>
<!ELEMENT orderby (order+) >
<!ELEMENT order (prop, (ascending | descending)?)
<!ATTLIST order casesensitive (1|0) "1" >
<!ELEMENT ascending EMPTY>
<!ELEMENT descending EMPTY>
<!ELEMENT limit (nresults) >
<!ELEMENT nresults (#PCDATA) >
This query retrieves the content length values for all resources located
under the server's "/container1/" URI namespace whose length exceeds 10000.
<d:searchrequest xmlns:d="DAV:">
<d:basicsearch>
<d:select>
<d:prop><d:getcontentlength/></d:prop>
</d:select>
<d:from>
<d:scope>
<d:href>/container1/</d:href>
<d:depth>infinity</d:depth>
</d:scope>
</d:from>
<d:where>
<d:gt>
<d:prop><d:getcontentlength/></d:prop>
<d:literal>10000</d:literal>
</d:gt>
</d:where>
<d:orderby>
<d:order>
<d:prop><d:getcontentlength/></d:prop>
<d:ascending/>
</d:order>
</d:orderby>
</d:basicsearch>
</d:searchrequest>
DAV:select defines the result record, which is a set of properties
and values. This document defines two possible values: DAV:allprop
and
DAV:prop, both defined in .
If the value is DAV:allprop, the result record for a given
resource includes all the properties for that resource.
If the value is DAV:prop, then the result record for a given
resource includes only those properties named by the DAV:prop
element. Each property named by the DAV:prop element must be referenced
in the Multistatus response.
The rules governing the status codes for each property match those of
the PROPFIND method defined in .
DAV:from defines the query scope. This contains exactly one DAV:scope
element.
The scope element contains a mandatory DAV:href element
and an optional DAV:depth element.
The scope element contains mandatory DAV:href and DAV:depth elements.
What should the default Depth value be for SEARCH?Agreement that Depth must be sent with SEARCH.DAV:href indicates the URI for a collection to use as a scope.
When the scope is a collection, if DAV:depth is "0", the search
includes only the collection. When it is "1", the search includes the (toplevel)
members of the collection. When it is "infinity", the search includes all
recursive members of the collection.
If the DAV:scope element is an absolute URI, the scope is exactly
that URI.
Allowing relative URIs isn't very useful.Accepted 24 April 2000.Need agreement on either forbidding relate URIs or leaving them in (which doesn't seem
to be hard to implement).Relative URI reference resolving code is required in WebDAV anyway, so the issue
is closed.If the DAV:scope element is a relative URI is an absolute URI reference, the scope is taken
to be relative to the request-URI.
A Scope can be an arbitrary URI.
Need to cleanup draft to use correct terms for URIs and URI references.Servers, of course, may support only particular scopes. This may include
limitations for particular schemes such as "http:" or "ftp:" or certain
URI namespaces.
If a scope is given that is not supported the server MUST respond with
a 400 status code that includes a Multistatus error. A scope in the query
appears as a resource in the response and must include an appropriate status
code indicating its validity with respect to the search arbiter.
Example:HTTP/1.1 400 Bad Request
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
<?xml version="1.0" encoding="UTF-8"?>
<d:multistatus xmlns:d="DAV:">
<d:response>
<d:href>http://www.foo.com/scope1</d:href>
<d:status>HTTP/1.1 502 Bad Gateway</d:status>
</d:response>
</d:multistatus>
This example shows the response if there is a scope error. The response
provides a Multistatus with a status for the scope. In this case, the scope
cannot be reached because the server cannot search another server (502).
DAV:where element defines the search condition for inclusion of
resources in the result set. The value of this element is an XML element
that defines a search operator that evaluates to one of the Boolean truth
values TRUE, FALSE, or UNKNOWN. The search operator contained by DAV:where
may itself contain and evaluate additional search operators as operands,
which in turn may contain and evaluate additional search operators as operands,
etc. recursively.
DAV:href isn't a property, so
it can't be used in queries. Is this a problem? Examples where DAV:displayname
is queried instead seem to indicate that. A possible solution would be
to allow DAV:href whereever DAV:prop is allowed in the where clause.
Each operator defined for use in the where clause that returns a Boolean
value MUST evaluate to TRUE, FALSE, or UNKNOWN. The resource under scan
is included as a member of the result set if and only if the search condition
evaluates to TRUE.
Consult Appendix A for details on the application of three-valued logic
in query expressions.
If a query contains an operator that is not supported by the server, then
the server MUST respond with a 422 (Unprocessable Entity) status code.
If a PROPFIND for a property value would yield a 404 or 403 response
for that property, then that property is considered NULL.
NULL values are "less than" all other values in comparisons.
Empty strings (zero length strings) are not NULL values. An empty string
is "less than" a string with length greater than zero.
The DAV:isdefined operator is defined to test if the value
of a property is NULL.
Comparisons of properties that do not have simple types (text-only content) is
out-of-scope for DAV:basicsearch. For querying the DAV:resourcetype property,
see .
The example shows a single operator (DAV:eq) applied in the criteria.
<d:where>
<d:eq>
<d:prop> <d:getcontentlength/> </d:prop>
<d:literal> 100 </d:literal>
</d:eq>
</d:where><d:where>
<d:eq>
<d:prop>
<d:getcontentlength/>
</d:prop>
<d:literal>100</d:literal>
</d:eq>
</d:where>
The example shows a more complex operation involving several operators
(DAV:and, DAV:eq, DAV:gt) applied in the criteria.
This DAV:where expression matches those resources that are "image/gifs"
over 4K in size.
<D:where>
<D:and>
<D:eq>
<D:prop> <D:getcontenttype/> </D:prop>
<D:literal> image/gif </D:literal>
</D:eq>
<D:gt>
<D:prop> <D:getcontentlength/> </D:prop>
<D:literal> 4096 </D:literal>
</D:gt>
</D:and>
</D:where><D:where>
<D:and>
<D:eq>
<D:prop>
<D:getcontenttype/>
</D:prop>
<D:literal>image/gif</D:literal>
</D:eq>
<D:gt>
<D:prop>
<D:getcontentlength/>
</D:prop>
<D:literal>4096</D:literal>
</D:gt>
</D:and>
</D:where>
The DAV:orderby element specifies the ordering of the result set.
It contains one or more DAV:order elements, each of which specifies
a comparison between two items in the result set. Informally, a comparison
specifies a test that determines whether one resource appears before another
in the result set. Comparisons are applied in the order they occur in the
DAV:orderby element, earlier comparisons being more significant.
Section 5.6 should have a separate section, with a separate heading,
for the description of ascending and descending. I had a hard time
finding these descriptions without this section heading.Added to index.The comparisons defined here use only a single property from each resource,
compared using the same ordering as the DAV:lt operator (ascending) or
DAV:gt operator (descending). If neither direction is specified,
the default is DAV:ascending.
In the WebDAV SEARCH spec (5.6, DAV:orderby), it says that nulls sort
low, to match SQL92.
However, SQL92 and SQL99 both say "Whether a sort key value that is
null is
considered greater or less than a non-null value is
implementation-defined,
but all sort key values that are null shall either be considered
greater than
all non-null values or be considered less than all non-null values."
(words taken from SQL99, 14.1 <declare cursor> General Rule 2)c), in
reference to null handling for the <order by clause>. )
I would note that in 5.5.3 WebDAV SEARCH says nulls are less than all
other values in a comparison, so the DAV:orderby matches that
statement,
it just gives an inaccurate reason.
In the context of the DAV:orderby element, null values are
considered to collate before any actual (i.e., non null) value, including
strings of zero length (
as in
as in ANSI standard SQL, [ANSISQL]).
XPath/XQuery (see draft,
and open issue)
specify string comparisons based on collations, not languages. I think we should
adopt this. This would mean that "xml:lang" would be removed, and an optional
attribute specifying the name of the collation is added.
Comparisons on strings take into account the language defined for that
property. Clients MAY specify the language using the xml:lang attribute.
If no language is specified either by the client or defined for that property
by the server or if a comparison is performed on strings of two different
languages, the results are undefined.
I think case-insensitive comparison is underspecified here (what does it mean for generic Unicode strings?)
The DAV:casesensitive attribute may be used to indicate case-sensitivity
for comparisons.
Servers SHOULD do caseless matching as defined in .
This sort orders first by last name of the author, and then by size, in
descending order, so that the largest works appear first.<d:orderby>
<d:order>
<d:prop><r:lastname/></d:prop>
<d:ascending/>
</d:order>
<d:order>
<d:prop><d:getcontentlength/></d:prop>
<d:descending/>
</d:order>
</d:orderby>
The DAV:and operator performs a logical AND operation on the expressions
it contains.
The DAV:or operator performs a logical OR operation on the
values it contains.
The DAV:not operator performs a logical NOT operation on the
values it contains.
How do string equality and language tag interact. Cross-language comparison should work at least when the two languages are dialects, e.g. en-us vs en-uk.Proposal: strings match if and only if they match character by character.
The DAV:eq operator provides simple equality matching on property
values.
The DAV:casesensitive attribute may be used with this element.
Define how comparisons on strings work, esp for i18n.
Need policy statement about sort order in various national languages. (JW said "non-Latin" but it's an issue even in languages that use the latin char set.)
The DAV:lt, DAV:lte, DAV:gt, and DAV:gte
operators provide comparisons on property values, using less-than, less-than
or equal, greater-than, and greater-than or equal respectively. The DAV:casesensitive
attribute may be used with these elements.
Dates (HTTPDate in getlastmodified).Agreement that it is OK to submit isodate to search HTTPDate (i.e., it's a marshalling issue only).Booleans appear to be underspecified in the specification. How is a boolean tested, and what are the behavior of operators like less than, greater than, etc.I think similar questions apply to booleans. Proposal: allow specification
of the literal's type using XML Schema simple types, and declare that "both" WebDAV date types are compatible.
The current DASL draft doesn't really have Booleans or any other data type.
It's trying to skate on data types. Booleans could be tested using the "eq"
and the combination "not eq", if you had well defined literals for TRUE and
FALSE. With the current syntax, that is the way you would have to test a
Boolean. Generally, Boolean values are not considered to be ordered, so "gt"
etc. wouldn't apply. However, if the literal values of a Boolean were 1 and
0 for TRUE and FALSE (using the most commonly used convention of positive
logic), then you would have an obvious ordering. 1 and 0 have the advantage
of being language independent. You now see a lot of electronic and
electro-mechanical devices (air conditioners, computers, etc.) with a "1/0"
label on the power switch, "1" meaning "on", and "0" meaning "off".
SQL databases don't have Booleans. SQL doesn't control DASL, of course, but
SQL databases are so widely used that they are important. The closest thing
in SQL is a bit field. Each bit in a bit field is zero or 1.
So, why not close the issue by saying: DASL doesn't have data types. You can
simulate Booleans by an integer data type, using 1 for "TRUE" and 0 for
"FALSE".
DAV:literal allows literal values to be placed in an expression.
How does xml:space affect DAV:literal.Do we just need an example here?Re-opened: see discussion in
DASL mailing list: using xml:space would
be inconsistent with WebDAV.
Because white space in literal values is significant in comparisons,
DAV:literal makes use of the xml:space attribute to identify this significance. The
default value of this attribute for DAV:literal is "preserve". Consult
section 2.10 of for more information on the use of this attribute.
White space in literal values is significant in comparisons. For consistency
with , clients SHOULD NOT specify the attribute "xml:space"
(section 2.10 of ) to override this behaviour.
The DAV:is-collection operator allows clients to determine whether a resource is
a collection (that is, whether it's DAV:resourcetype element contains the
element DAV:collection).
Rationale: This operator is provided in lieu of defining generic
structure queries, which would suffice for this and for many more powerful
queries, but seems inappropriate to standardize at this time.
Update DTD and move up to the other operators.
This example shows a search criterion that picks out all and only the resources
in the scope that are collections.
<where xmlns="DAV:">
<is-collection/>
</where>
The DAV:isdefined operator allows clients to determine whether
a property is defined on a resource. The meaning of "defined on a resource"
is found in .
Example:<d:isdefined>
<d:prop><x:someprop/></d:prop>
</d:isdefined>The DAV:isdefined operator is optional.
The DAV:like is an optional operator intended to give simple wildcard-based
pattern matching ability to clients.
The operator takes two arguments.
The first argument is a DAV:prop element identifying a single
property to evaluate.
The semantics of DAV:literal should not change inside a DAV:like.Does it? Need details.Closed; I think this is clear from the spec.The second argument is a DAV:literal element that gives the
pattern matching string.
Pattern := [wildcard] 0*( text [wildcard] )
wildcard := exactlyone | zeroormore
text := 1*( <octet> | escapesequence )
exactlyone : = "?"
zeroormore := "%"
escapechar := "\"
escapesequence := "\" ( exactlyone | zeroormore | escapechar )Pattern := [wildcard] 0*( text [wildcard] )
wildcard := exactlyone | zeroormore
text := 1*( <character> | escapesequence )
exactlyone : = "?"
zeroormore := "%"
escapechar := "\"
escapesequence := "\" ( exactlyone | zeroormore | escapechar )
character: see section 2.2 of [XML]
The BNF for a wildcard permits the entry of "</d:literal>" which
would confuse parsers. Also, the BNF sequence for text should use
characters instead of octets, to better handle multi-octet character
set representations (like UTF-16).
Non-issue: the contents of the DAV:literal element is subject to normal XML escaping.
Grammar changed to use chars rather than octets.
The value for the literal is composed of wildcards separated by segments
of text. Wildcards may begin or end the literal. Wildcards may not be adjacent.
The "?" wildcard matches exactly one character.
The "%" wildcard matches zero or more characters
The "\" character is an escape sequence so that the literal can include
"?" and "%". To include the "\" character in the pattern, the escape sequence
"\\" is used..
This example shows how a client might use DAV:like to identify
those resources whose content type was a subtype of image.
<D:where>
<D:like>
<D:prop><D:getcontenttype/></D:prop>
<D:literal>image%</D:literal>
</D:like>
</D:where>5.13 should discuss handling of queries when character set differs.
Some text on handling character sets would be helpful.
The DAV:contains operator is an optional operator that provides
content-based search capability. This operator implicitly searches against
the text content of a resource, not against content of properties. The
DAV:contains
operator is intentionally not overly constrained, in order to allow the
server to do the best job it can in performing the search.
The DAV:contains operator evaluates to a Boolean value. It
evaluates to TRUE if the content of the resource satisfies the search.
Otherwise, It evaluates to FALSE.
Within the DAV:contains XML element, the client provides a
phrase: a single word or whitespace delimited sequence of words. Servers
MAY ignore punctuation in a phrase. Case-sensitivity is left to the server.
The following things may or may not be done as part of the search: Phonetic
methods such as "soundex" may or may not be used. Word stemming may or
may not be performed. Thesaurus expansion of words may or may not be done.
Right or left truncation may or may not be performed. The search may be
case insensitive or case sensitive. The word or words may or may not be
interpreted as names. Multiple words may or may not be required to be adjacent
or "near" each other. Multiple words may or may not be required to occur
in the same order. Multiple words may or may not be treated as a phrase.
The search may or may not be interpreted as a request to find documents
"similar" to the string operand.
The DAV:score property is intended to be useful to rank documents
satisfying the DAV:contains operator.
The example below shows a search for the phrase "Peter Forsberg".
Depending on its support for content-based searching, a server MAY treat
this as a search for documents that contain the words "Peter" and "Forsberg".
<D:where>
<D:contains>Peter Forsberg</D:contains>
</D:where>
The example below shows a search for resources that contain "Peter" and
"Forsberg".
<D:where>
<D:and>
<D:contains>Peter</D:contains>
<D:contains>Forsberg</D:contains>
</D:and>
</D:where><!ELEMENT limit (nresults) >
The DAV:limit XML element contains requested limits from the client
to limit the size of the reply or amount of effort expended by the server.
<!ELEMENT nresults (#PCDATA)> ;only digitsOn the topic of partial search results, DASL currently has no way
for a client to request the next chunk of a set of search results.
Since *every* search service I've interacted with on the Internet
has a feature for returning the next set of search results, I really
would expect this feature to be in DASL. An explanation for why this
feature isn't present should be in the protocol specification if it
is not going to be supported.
of course this issue is legitim. However, as basicsearch should be as simple
as possible, I tend to say out of scope as well. But perhaps this could be
an optional feature (is it that, what you mean by extension to
DAV:basicsearch)?
Moved into DAV:basicsearch section, because this is a request for a specific
query grammar feature.
The DAV:nresults XML element contains a requested maximum number
of records to be returned in a reply. The server MAY disregard this limit.
The value of this element is an integer.
The attribute probably should be renamed to "caseless".
The DAV:casesensitive attribute allows clients to specify case-sensitive
or case-insensitive behavior for DAV:basicsearch operators.
The possible values for DAV:casesensitive are "1" or "0". The
"1" value indicates case-sensitivity. The "0" value indicates case-insensitivity.
The default value is server-specified.
Case-insensitivity SHOULD implemented using caseless matching as defined in .
Support for the DAV:casesensitive is optional. A server should
respond with an error 422 if the DAV:casesensitive attribute is
used but cannot be supported.
<!ELEMENT score (#PCDATA)>
The DAV:score XML element is a synthetic property whose value
is defined only in the context of a query result where the server computes
a score, e.g. based on relevance. It may be used in DAV:select
or DAV:orderby elements. Servers SHOULD support this property.
The value is a string representing the score, an integer from zero to 10000
inclusive, where a higher value indicates a higher score (e.g. more relevant).
Clients should note that, in general, it is not meaningful to compare
the numeric values of scores from two different query results unless both were
executed by the same underlying search system on the same collection of
resources.Shouldn't be done using a pseudo-property. Report
it as child of DAV:propstat instead?<!ELEMENT iscollection (#PCDATA)>
The DAV:iscollection XML element is a synthetic property whose
value is defined only in the context of a query.
The property is TRUE (the literal string "1") of a resource if and only
if a PROPFIND of the DAV:resourcetype property for that resource
would contain the DAV:collection XML element. The property is
FALSE (the literal string "0") otherwise.
Rationale: This property is provided in lieu of defining generic
structure queries, which would suffice for this and for many more powerful
queries, but seems inappropriate to standardize at this time.
DAV:iscollection should be an operator rather than a pseudo-property. This both reduces special cases in implementations and avoids confusion with real properties.
This example shows a search criterion that picks out all and only the resources
in the scope that are collections.
<D:where>
<D:eq>
<D:prop><D:iscollection></D:prop>
<D:literal>1<D:literal>
</D:eq>
</D:where>(1) DTD needs to be cleaned up, (2) there should be a way to advertise propdescs for all properties not mentioned otherwise.
The DAV:basicsearch grammar defines a search criteria that is
a Boolean-valued expression, and allows for an arbitrary set of properties
to be included in the result record. The result set may be sorted on a
set of property values. Accordingly the DTD for schema discovery for this
grammar allows the server to express:
the set of properties that may be either searched, returned, or used
to sort, and a hint about the data type of such propertiesthe set of optional operators defined by the resource.<!ELEMENT basicsearchschema (properties, operators)>
<!ELEMENT properties (propdesc*)>
<!ELEMENT propdesc (prop, ANY)>
<!ELEMENT operators (opdesc*)>
<!ELEMENT opdesc ANY>
<!ELEMENT operand_property EMPTY>
<!ELEMENT operand_literal EMPTY><!ELEMENT basicsearchschema (properties, operators)>
<!ELEMENT any-other-property EMPTY>
<!ELEMENT properties (propdesc*)>
<!ELEMENT propdesc (prop|any-other-property), datatype?,
searchable?, selectable?, sortable?,
casesensitive?)>
<!ELEMENT operators (opdesc*)>
<!ELEMENT opdesc ANY>
<!ELEMENT operand-literal EMPTY>
<!ELEMENT operand-property EMPTY>
To stay consistent with other WebDav specs, I'd prefer to use "-" instead of "_" as separator.
The DAV:properties element holds a list of descriptions of properties.
The DAV:operators element describes the optional operators
that may be used in a DAV:where element.
Each instance of a DAV:propdesc element describes the property
or properties in the DAV:prop element it contains. All subsequent
elements are descriptions that apply to those properties. All descriptions
are optional and may appear in any order. Servers SHOULD support all the
descriptions defined here, and MAY define others.
DASL defines five descriptions. The first, DAV:datatype, provides
a hint about the type of the property value, and may be useful to a user
interface prompting for a value. The remaining four (DAV:searchable,
DAV:selectable,
DAV:sortable, and DAV:casesensitive)
identify portions of the query (DAV:where,
DAV:select,
and DAV:orderby, respectively). If a property has a description
for a section, then the server MUST allow the property to be used in that
section. These descriptions are optional. If a property does not have such
a description, or is not described at all, then the server MAY still allow
the property to be used in the corresponding section.
This element can be used in place of DAV:prop to describe properties of
WebDAV properties not mentioned in any other DAV:prop element. For instance,
this can be used to indicate that all other properties are searchable and selectable
without giving details about their types (a typical scenario for dead properties).Should use standard datatypes from XML Schema Part 2 and also allow for user-defined types.
The DAV:datatype element contains a single XML element that provides
a hint about the domain of the property, which may be useful to a user
interface prompting for a value to be used in a query.
The namespace for expressing a DASL defined data type is "urn:uuid:C2F41010-65B3-11d1-A29F-00AA00C14882/".
Datatypes are identified by an element name. Where appropriate, a server SHOULD
use the simple datatypes defined in .
<!ELEMENT datatype ANY >
Examples from , section 3:
Qualified name Example
xs:boolean true, false, 1, 0
xs:string Foobar
xs:dateTime 1994-11-05T08:15:5Z
xs:float .314159265358979E+1
xs:integer -259, 23
DASL defines the following data type elements:
Name Example
boolean 1, 0
string Foobar
dateTime.iso8601tz 1994-11-05T08:15:5Z
float .314159265358979E+1
int -259, 23
If the data type of a property is not given, then the data type defaults
to
xs:string.
<!ELEMENT searchable EMPTY>
If this element is present, then the server MUST allow this property to
appear within a DAV:where element where an operator allows a property.
Allowing a search does not mean that the property is guaranteed to be defined
on every resource in the scope, it only indicates the server's willingness
to check.
<!ELEMENT selectable EMPTY>
This element indicates that the property may appear in the DAV:select
element.
This element indicates that the property may appear in the DAV:orderby
element.
<!ELEMENT sortable EMPTY>
This element only applies to properties whose data type is "xs:string"
and derived data types
as
per the DAV:datatype property description. Its presence indicates
that compares performed for searches, and the comparisons for ordering
results on the string property will be case sensitive. (The default is
case insensitive.)
<!ELEMENT casesensitive EMPTY>
The DAV:operators element describes every optional operator supported
in a query. (Mandatory operators are not listed since they are mandatory
and permit no variation in syntax.). All optional operators that are supported
MUST be listed in the DAV:operators element. The listing for an
operator consists of the operator (as an empty element), followed by one
element for each operand. The operand MUST be either
DAV:operand_property or DAV:operand_literal,DAV:operand-property or DAV:operand-literal,
which indicate that the operand in the
corresponding position is a property or a literal value, respectively.
If an operator is polymorphic (allows more than one operand syntax) then
each permitted syntax MUST be listed separately.
<D:propdesc>
<D:like/><D:operand_property/><D:operand_literal/>
</D:propdesc><operators xmlns='DAV:'>
<opdesc>
<like/><operand-property/><operand-literal/>
</opdesc>
</operators>
<D:basicsearchschema xmlns:D="DAV:"
xmlns:t="urn:uuid:C2F41010-65B3-11d1-A29F-00AA00C14882/"
xmlns:J="http://jennicam.org">
<D:properties>
<D:propdesc>
<D:prop><D:getcontentlength/></D:prop>
<D:datatype><t:int/></D:datatype>
<D:searchable/><D:selectable/><D:sortable/>
</D:propdesc>
<D:propdesc>
<D:prop><D:getcontenttype/><D:displayname/></D:prop>
<D:searchable/><D:selectable/> <D:sortable/>
</D:propdesc>
<D:propdesc>
<D:prop><J:fstop/></D:prop>
<D:selectable/>
</D:propdesc>
</D:properties>
<D:operators>
<D:opdesc>
<D:isdefined/><D:operand_property/>
</D:opdesc>
<D:opdesc>
<D:like/><D:operand_property/><D:operand_literal/>
</D:opdesc>
</D:operators>
</D:basicsearchschema><D:basicsearchschema xmlns:D="DAV:"
xmlns:xs="http://www.w3.org/2001/XMLSchema"">
<D:properties>
<D:propdesc>
<D:prop><D:getcontentlength/></D:prop>
<D:datatype><xs:nonNegativeInteger/></D:datatype>
<D:searchable/><D:selectable/><D:sortable/>
</D:propdesc>
<D:propdesc>
<D:prop><D:getcontenttype/><D:displayname/></D:prop>
<D:searchable/><D:selectable/><D:sortable/>
</D:propdesc>
<D:propdesc>
<D:prop><fstop xmlns="http://jennicam.org"/></D:prop>
<D:selectable/>
</D:propdesc>
<D:propdesc>
<D:any-other-property/>
<D:searchable/><D:selectable/>
</D:propdesc>
</D:properties>
<D:operators>
<D:opdesc>
<D:isdefined/><D:operand-property/>
</D:opdesc>
<D:opdesc>
<D:like/><D:operand-property/><D:operand-literal/>
</D:opdesc>
</D:operators>
</D:basicsearchschema>
This response lists four properties. The datatype of the last three properties
is not given, so it defaults to xs:string. All are selectable, and the first
three may be searched. All but the last may be used in a sort. Of the optional
DAV operators, DAV:isdefined and DAV:like are supported.
Note: The schema discovery defined here does not provide for
discovery of supported values of the DAV:casesensitive attribute.
This may require that the reply also list the mandatory operators.
Clients have the opportunity to tag properties when they are stored in
a language. The server SHOULD read this language-tagging by examining the
xml:lang attribute on any properties stored on a resource.
The xml:lang attribute specifies a nationalized collation sequence when
properties are compared.
Comparisons when this attribute differs have undefined order.
In Security Considerations, copy XML considerations from webDAV spec.Wouldn't it be better to just cite the XML document, so that if that document is updated, we won't have stale information?In Security Considerations, mention privacy risks of queries.Is this resolved?
This section is provided to detail issues concerning security implications
of which DASL applications need to be aware. All of the security considerations
of HTTP/1.1 also apply to DASL. In addition, this section will include
security risks inherent in searching and retrieval of resource properties
and content.
A query must not allow one to retrieve information about values or existence
of properties that one could not obtain via PROPFIND. (e.g. by use in DAV:orderby,
or in expressions on properties.)
A server should prepare for denial of service attacks. For example a
client may issue a query for which the result set is expensive to calculate
or transmit because many resources match or must be evaluated. 7.1 Implications
of XML External Entities
XML supports a facility known as "external entities", defined in section
4.2.2 of , which instruct an XML processor to retrieve and perform
an inline include of XML located at a particular URI. An external XML entity
can be used to append or modify the document type declaration (DTD) associated
with an XML document. An external XML entity can also be used to include
XML within the content of an XML document. For non-validating XML, such
as the XML used in this specification, including an external XML entity
is not required by . However, does state that an XML
processor may, at its discretion, include the external XML entity.
External XML entities have no inherent trustworthiness and are subject
to all the attacks that are endemic to any HTTP GET request. Furthermore,
it is possible for an external XML entity to modify the DTD, and hence
affect the final form of an XML document, in the worst case significantly
modifying its semantics, or exposing the XML processor to the security
risks discussed in . Therefore, implementers must be aware that
external XML entities should be treated as untrustworthy.
There is also the scalability risk that would accompany a widely deployed
application which made use of external XML entities. In this situation,
it is possible that there would be significant numbers of requests for
one external XML entity, potentially overloading any server which fields
requests for the resource containing the external XML entity.
Query grammars are identified by URIs. Applications SHOULD not attempt
to retrieve these URIs even if they appear to be retrievable (for example,
those that begin with "http://")
Authentication mechanisms defined in WebDAV will also apply to DASL.
This document uses the namespace defined by for XML elements.
All other IANA considerations mentioned in also applicable to
DASL.
To be supplied.
To be supplied.
Hypertext Transfer Protocol -- HTTP/1.1University of California, Irvine, Information and Computer ScienceIrvineCA92697-3425US+1 949 824 1715fielding@ics.uci.eduWorld Wide Web Consortium, MIT Laboratory for Computer Science545 Technology SquareCambridgeMA02139US+1 617 258 8682jg@w3.orgCompaq Computer Corporation, Western Research Laboratory250 University AvenuePalo AltoCA94301USmogul@wrl.dec.comWorld Wide Web Consortium, MIT Laboratory for Computer Science545 Technology SquareCambridgeMA02139US+1 617 258 8682frystyk@w3.orgXerox Corporation3333 Coyote Hill RoadPalo AltoCA94034USmasinter@parc.xerox.comMicrosoft Corporation1 Microsoft WayRedmondWA98052USpaulle@microsoft.comWorld Wide Web Consortium, MIT Laboratory for Computer Science545 Technology SquareCambridgeMA02139US+1 617 258 8682timbl@w3.orgThe Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, collaborative, hypermedia information systems. It is a generic, stateless, protocol which can be used for many tasks beyond its use for hypertext, such as name servers and distributed object management systems, through extension of its request methods, error codes and headers. A feature of HTTP is the typing and negotiation of data representation, allowing systems to be built independently of the data being transferred.HTTP has been in use by the World-Wide Web global information initiative since 1990. This specification defines the protocol referred to as "HTTP/1.1", and is an update to RFC 2068.Key words for use in RFCs to Indicate Requirement LevelsHarvard University1350 Mass. Ave.CambridgeMA 02138- +1 617 495 3864-
General
keyword
In many standards track documents several words are used to signify
the requirements in the specification. These words are often
capitalized. This document defines these words as they should be
interpreted in IETF documents. Authors who follow these guidelines
should incorporate this phrase near the beginning of their document:
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
RFC 2119.
Note that the force of these words is modified by the requirement
level of the document in which they are used.
Extensible Markup Language (XML) 1.0 (2nd ed)Textuality and Netscapetbray@textuality.comMicrosoftjeanpa@microsoft.comUniversity of Illinois at Chicago and Text Encoding Initiativecmsmcq@uic.eduSun Microsystemseve.maler@east.sun.comNamespaces in XMLTextualitytbray@textuality.comHewlett-Packard Companydmh@corp.hp.comMicrosoftandrewl@microsoft.comXML Schema Part 2: DatatypesKaiser Permanente, for Health Level SevenPaul.V.Biron@kp.orgMicrosoft, formerly of IBMashokma@microsoft.comWorld Wide Web ConsortiumMIT Laboratory for Computer Science545 Technology SquareCambridgeMA02139US+ 1 617 253 2613+ 1 617 258 5999timbl@w3.orghttp://www.w3c.orgHTTP Extensions for Distributed Authoring -- WEBDAVMicrosoft Corporationyarong@microsoft.comDept. Of Information and Computer Science, University of California, Irvineejw@ics.uci.eduNetscapeasad@netscape.comNovellsrcarter@novell.comNovelldcjensen@novell.comVersioning Extensions to WebDAVRational Softwaregeoffrey.clemm@rational.comIBMjamsden@us.ibm.comIBMtim_ellison@uk.ibm.comMicrosoftckaler@microsoft.comUC Santa Cruz, Dept. of Computer Scienceejw@cse.ucsc.eduWebDAV Access Control ProtocolRational Softwaregeoffrey.clemm@rational.comMicrosoft Corporationannehop@microsoft.comOracle Corporationesedlar@us.oracle.comUC Santa Cruz, Dept. of Computer Scienceejw@cse.ucsc.eduXML Media TypesIBM Tokyo Research Laboratorymmurata@trl.ibm.co.jpsimonstl.comsimonstl@simonstl.comSkymoon Venturesdan@dankohn.comDatabase Language SQL Part 2: Foundation (SQL/Foundation)International Organization for StandardizationCase MappingsIBMmark.davis@us.ibm.comRequirements for DAV Searching and LocatingCourseNet Systems170 Capp StreetSan FranciscoCA94110jrd3@alum.mit.eduMicrosoftOne Microsoft WayRedmondWA9085-6933saveenr@microsoft.comXerox Corporation800 Phillips Road 128-29Eslein@wrc.xerox.comDAV Searching & LocatingMicrosoftOne Microsoft WayRedmondWA9085-6933saveenr@microsoft.comNovell1555 N. Technology Way, M/S ORM-M-314OremUT84097dlowry@novell.comOracle Corporation600 Oracle Parkway, M/S 6op3RedwoodshoresCA94065+1 650 506 5441skreddy@us.oracle.comNetscaperickh@netscape.comIntelligent Markets410 Jessie Street 6th floorSan FranciscoCA94103jrd3@alum.mit.eduFilenet3565 Harbor Blvd.Costa MesaCA92626+1 714 966 3403ababich@filenet.com
ANSI standard three valued logic is used when evaluating the search condition
(as defined in the ANSI standard SQL specifications, for example in ANSI
X3.135-1992, section 8.12, pp. 188-189, section 8.2, p. 169, General Rule
1)a), etc.).
ANSI standard three valued logic is undoubtedly the most widely practiced
method of dealing with the issues of properties in the search condition
not having a value (e.g., being null or not defined) for the resource under
scan, and with undefined expressions in the search condition (e.g., division
by zero, etc.). Three valued logic works as follows.
Undefined expressions are expressions for which the value of the expression
is not defined. Undefined expressions are a completely separate concept
>from the truth value UNKNOWN, which is, in fact, well defined. Property
names and literal constants are considered expressions for purposes of
this section. If a property in the current resource under scan has not
been set to a value (either because the property is not defined for the
current resource, or because it is null for the current resource), then
the value of that property is undefined for the resource under scan. DASL
1.0 has no arithmetic division operator, but if it did, division by zero
would be an undefined arithmetic expression.
If any subpart of an arithmetic, string, or datetime subexpression is
undefined, the whole arithmetic, string, or datetime subexpression is undefined.
There are no manifest constants to explicitly represent undefined number,
string, or datetime values.
Since a Boolean value is ultimately returned by the search condition,
arithmetic, string, and datetime expressions are always arguments to other
operators. Examples of operators that convert arithmetic, string, and datetime
expressions to Boolean values are the six relational operators ("greater
than", "less than", "equals", etc.). If either or both operands of a relational
operator have undefined values, then the relational operator evaluates
to UNKNOWN. Otherwise, the relational operator evaluates to TRUE or FALSE,
depending upon the outcome of the comparison.
The Boolean operators DAV:and, DAV:or and DAV:not
are evaluated according to the following rules:
UNKNOWN and UNKNOWN = UNKNOWN
UNKNOWN or UNKKNOWN = UNKNOWN
not UNKNOWN = UNKNOWN
UNKNOWN and TRUE = UNKNOWN
UNKNOWN and FALSE = FALSE
UNKNOWN and UNKNOWN = UNKNOWN
UNKNOWN or TRUE = TRUE
UNKNOWN or FALSE = UNKNOWN
UNKNOWN or UNKNOWN = UNKNOWN
Initial Draft
Referring to DASL as an extension to HTTP/1.1 rather than DAV.
Added new sections "Notational Conventions", "Protocol Model", "Security
Considerations".
Changed section 3 to "Elements of Protocol".
Added some stuff to introduction.
Added "result set" terminology.
Added "IANA Considerations".
Moved sub-headings of "Elements of Protocol" to first level and removed
"Elements of Protocol" Heading.
Added an sentence in introduction explaining that this is a "sketch"
of a protocol.
Added orderby, data typing, three valued logic, query schema property,
and element definitions for schema for basicsearch.
- made changes based on last week's DASL BOF.
Removed most of DAV:searcherror; converted to DAV:searchredirect
Altered DAV:basicsearch grammar to use avoid use of ANY in DTD
-Added details on Query Schema Discovery
-Shortened list of data types
moved data types before change history
rewrote the data types section
removed the casesensitive element and replace with the casesensitive
attribute
added the casesensitive attribute to the DTD for all operations that
might work on a string
A series of changes. See Author's meeting minutes for details.
Changes as per author's meeting. QSD uses SEARCH, not PROPFIND.
Moved text around to keep concepts nearby.
Boolean literals are 1 and 0, not T and F.
contains changed to contentspassthrough.
Renamed rank to score.
Added Dale Lowry as Author
Added 422 as response when query lists unimplemented operators.
DAV:literal declares a default value for xml:space, 'preserve'
(see XML spec, section 2.10)
moved to new XML namespace syntax
Changed "simplesearch" to "basicsearch"
Changed isnull to isdefined
Defined NULLness as having a 404 or 403 response
used ENTITY syntax in DTD
Added redirect
Fixed a series of typographical and formatting errors.
Modified the section of three-valued logic to use a table rather than
a text description of the role of UNKNOWN in expressions.
Added the DAV:contains operator.
Removed the DAV:contentpassthrough operator.
Various author comments for submission
Cosmetic and minor editorial changes only. Fix nits reported by Jim Whitehead
in email of April 26, 1999. Converted to HTML from Word 97, manually.
Removed redirection feature, since 301/302 suffices. Removed Query Schema Discovery (former chapter 4). Everyone agrees this is a useful feature, but it is apparently too difficult to define at this time, and it is not essential for DASL.
Added Julian Reschke as author.
Chapter about QSD re-added.
Formatted into RFC2629-compliant XML document.
Added first comments.
ID version number kicked up to draft-dasl-protocol-03.
Updated address information for Jim Davis.
Added issue of datatype vocabularies.
Updated issue descriptions for grammar discovery,
added issues on query schema DTD.
Fixed typos in XML examples.
Re-introduced split between normative and non-normative references.
Version bumbed up to 04. Started work on resolving the issues identified
in the previous version.
Fixed some XML typos.
Closed issues naming-of-elements. Fixed query search DTD and added option
to discover properties of "other" (non-listed) properties.
Changed into private submission and added reference to historic DASL draft.
Marked reference to DASL requirements non-normative.
Updated reference to latest deltav spec.
Added feedback from and updated contact info for Alan Babich.
Included open issues collected in http://www.webdav.org/dasl/protocol/issues.html.
Made sure that all artwork fits into 72 characters wide text.
Changed Insufficient storage handling (multistatus). Moved is-collection to
operators and added to DTD. Made scope/depth mandatory.
Updated reference to SQL99.
"Non-normative References" -> "Informative References". Abstract updated.
Consistently specify a charset when using text/xml (no change bars). Do
not attempt to define PROPFIND's entity encoding (take out specific references
to text/xml). Remove irrelevant headers (Connection:) from examples (no
change bars). Added issue on querying based on DAV:href. Updated introduction
to indicate relationship to DASL draft. Updated HTTP reference from
RFC2068 to RFC2616. Updated XML reference to XML 1.0 2nd edition.
Removed superfluous namespace decl in 2.4.2. Reopened JW14 and suggest
to drop xml:space support.
Removed "xml:space" feature on DAV:literal. Added issue about string
comparison vs. collations vs. xml:lang. Updated some of the open issues
with details from JimW's original mail in April 1999. Resolved scope vs
relative URI references. Resolved issues about DAV:ascending (added to
index) and the BNF for DAV:like (changed "octets" to "characters").
Updated reference to DeltaV (now RFC3253). Added Martin Wallmer's comments,
moved JW5 into DAV:basicsearch section.
Closed open issues regaring the type of search arbiters (JW3) and their
discovery (JW9). Rephrased requirements on multistatus response bodies
(propstat only if properties were selected, removed requirement for
responsedescription).
RFC2376 -> RFC3023. Added missing first names of authors. OPTIONS added
to example for DAV:supported-method-set.