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RE: New properties (metadata) draft

From: Yaron Goland <yarong@microsoft.com>
Date: Mon, 16 Jun 1997 18:23:47 -0700
Message-ID: <11352BDEEB92CF119F3F00805F14F48502EE9C67@RED-44-MSG.dns.microsoft.com>
To: "'Jim Whitehead'" <ejw@rome.ICS.UCI.EDU>, w3c-dist-auth@w3.org
Two of the examples have erroneously specified namespace values and the
Entity-Name entry in section 8.1 was not correct. The correct entries
are given below.

6.3.11	Example
		PATCH bar;DAV/ HTTP/1.1
		Host: www.foo.com
		Content-Type: application/XML
		Content-Length: xxxx

		<XML>

<XML:Namespace><Ref>http://www.w3.com/standards/dublin/</><AS>D</></>

<XML:Namespace><Ref>http://www.ietf.org/standards/dav/patch/</><AS>P</><
/>

<XML:Namespace><Ref>http://www.w3.com/standards/z39.50/</><AS>Z</></>
			
			<P:PropertyUpdate>
				<Create>
					<XML:Ref>Z:authors</>
					<PatchValue>
						<Author>Jim Whitehead</>
						<Author>Roy Fielding</>
					</>	
				</>
				<Remove><Ref>D:Copyright-Onwer</></>
				<Insert>

<InsertPoint><Position>Before</><XML:Ref>Z:producer</></>

<InsertName><XML:Ref>Z:Last-Modified</></>
					<PatchValue></>
				</>
				<Insert>

<InsertPoint><Position>After</><XML:Ref>Z:editor(1)</></>

<InsertName><XML:Ref>Z:editor</></>
				</>
</>	</>

6.5.4	Example
		SEARCH  /container/ HTTP/1.1
		Host: www.foo.bar
		Content-Length: xxxx
		Content-Type: application/xml

		<XML>

<XML:Namespace><Ref>http://www.ietf.org/standards/dav/search/</><AS>S</>
</>
			<S:limited-search><OR><AND><Name>*</></></></>
		</>

		HTTP/1.1 200 OK
		Content-Type: application/xml
		Content-Length: xxxxx

		<XML>

<XML:Namespace><Ref>http://www.ietf.org/standards/dav/search/</>S</>

<XML:Namespace><Ref>http://www.foo.bar/container</><AS>R</></>

<XML:Namespace><Ref>http://www.aiis.org/standards/dav/</><AS>A</>
			<S:SearchResult>
				<XML:Namespace><Ref>R:(A)</><AS>RA</></>
				<RA:author><D:live></>Jim Whitehead</>

<XML:Namespace><Ref>R:/member1/(A)</><AS>M1</></>
				<M1:author><D:live></>Roy Fielding</>
		</>	</>


8.1
Entity-Name = ([As-Tag ":"] Name) | (As-Tag ":")

				Yaron

> -----Original Message-----
> From:	Jim Whitehead [SMTP:ejw@rome.ICS.UCI.EDU]
> Sent:	Monday, June 16, 1997 4:47 PM
> To:	w3c-dist-auth@w3.org
> Subject:	New properties (metadata) draft
> 
> 
> Enclosed is the text of a new draft which satisfies the requirements
> for attributes (Section 5.1 of the requirements document), linking
> (Section 5.2 of the requirements), and retrieval of unprocessed source
> (Requirements Section 5.5).  In this draft, an instance of a piece of
> metadata is known as a property.  This draft differs from the previous
> draft on metadata operations (the GETMETA, ADDMETA, DELMETA draft) in
> that it uses GET to retrieve properties, and employs new PATCH method
> to add and delete property values.  A SEARCH method provides the
> capability to search properties.
> 
> This draft also makes use of the Extended Markup Language (XML) as an
> on-the-wire representation for property names and values.  Due to the
> recent release of the Meta Content Framework (MCF) draft, and the
> similarity between MCF and the XML representation given in this draft,
> there is currently debate within the Design Team over whether the
> on-the-wire representation should use MCF.  The primary affect of this
> debate is limited to Section 2.7, Visualizing a Property Tree Using
> XML, which gives an algorithm for converting properties to an XML
> representation, although it would also affect the examples throughout.
> 
> Since the XML specification has not yet been finalized (although there
> is
> considerable agreement on most of its features) this draft has
> provided
> a description of the subset of XML which is used within the
> specification.
> This description occurs towards the end of the specification, in
> Appendicies 1-5.  It also appears that this spec. mistakenly uses the
> term "XML entity" instead of "XML element."
> 
> 
> The properties draft is available at URL:
> http://www.ics.uci.edu/~ejw/authoring/proposals/properties.html
> 
> The latest XML specification is available at URL:
> http://www.textuality.com/sgml-erb/WD-xml-lang.html
> 
> The MCF proposal is available at URL:
> http://developer.netscape.com/mcf.html
> 
> 
> Your comments and ideas on this draft are definitely appreciated.
> 
> - Jim
> 
> 
> 
>                A Data Model and Operations for DAV Properties
> 
> Version 0.1, June 16, 1997
> 
> 1 Introduction
> 
> 1.1 Introduction
> 
> Properties are pieces of data that describe the state of a resource.
> Properties are data about data. The term property is used within this
> proposal to disambiguate the concept from the overloaded terms
> "metadata"
> and "attribute".
> 
> Properties are used within distributed authoring environments to
> provide for
> efficient discovery and management of resources. For example, a
> subject
> property allows for the indexing of all resources by their subject and
> an
> author property allows for the discovery of what authors have written
> which
> documents. As explored in the next section, properties have a long
> history,
> having proven themselves essential to the maintenance of large
> document
> repositories.
> 
> 1.2 Existing Metadata Proposals
> 
> Many current proposals contain some notion of a property. These
> include PICS
> [Miller et al., 1996], PICS-NG, the Rel/Rev draft [Maloney, 1996], Web
> Collections, XML [Bray, 1997], several proposals on representing
> relationships within HTML, digital signature manifests (DCMF), and a
> position paper on Web metadata architecture [Berners-Lee, 1997].
> 
> Some proposals come from a digital library perspective. These include
> the
> Dublin Core [Weibel et al., 1995] metadata set and the Warwick
> Framework
> [Lagoze, 1996], a container architecture for different metadata
> schemas. The
> literature includes many examples of metadata, including MARC [MARC,
> 1994],
> a bibliographic metadata format, RFC 1807 [Lasher, Cohen, 1995], a
> technical
> report bibliographic format employed by the Dienst system, and the
> proceedings from the first IEEE Metadata conference describe many
> community-specific metadata sets.
> 
> Participants of the 1996 Metadata II Workshop in Warwick, UK [Lagoze,
> 1996],
> noted that, "new metadata sets will develop as the networked
> infrastructure
> matures" and "different communities will propose, design, and be
> responsible
> for different types of metadata." These observations can be
> corroborated by
> noting that many community-specific sets of metadata already exist,
> and
> there is significant motivation for the development of new forms of
> metadata
> as many communities increasingly make their data available in digital
> form,
> requiring a metadata format to assist data location and cataloging.
> 
> 1.3 Properties and HTTP Headers
> 
> Properties already exist, to a certain extent, within HTTP through the
> use
> of message headers. However, in distributed authoring environments a
> relatively large number of properties are needed to fully describe the
> state
> of a resource and setting/returning them all through HTTP headers is
> inefficient. Thus a mechanism is needed which allows a principal to
> identify
> a set of properties in which the principal is interested and to then
> set or
> retrieve just those properties.
> 
> 1.4 Why Another Draft?
> 
> Given that this is the fourth major draft on metadata capabilities
> submitted
> to the WebDAV working group, a reasonable question to ask is, "Why
> another
> draft?" In short, the following limitations in "A Proposal for Web
> Metadata
> Operations" [WebDAV, 1997] led to the development of this new
> proposal:
> 
> Poor Internationalization Support. While the simple name/value pairs
> in
> [WebDAV, 1997] do allow the value field to contain an arbitrary
> sequence of
> octets, there is no way to indicate their character encoding.
> 
> No Typing Support. Similar to the internationalization support, there
> is no
> way to indicate the encoding of binary data in a value field in
> [WebDAV,
> 1997], for example, to indicate a sequence of octets should be viewed
> as an
> integer, or as a floating point number,
> 
> Proliferation of Methods. Since [WebDAV, 1997] does not contain a
> naming
> mechanism that combines the name of the resource and the name of the
> property into a single name, the methods GETMETA, DELMETA, and ADDMETA
> are
> necessary to "glue" together the name of the resource and the name of
> the
> property.
> 
> No Sub-Properties. In [WebDAV, 1997] there is no way to define a
> property
> which describes another property (i.e., data about properties), yet
> this
> facility is useful for refining the meaning of a property. One
> important use
> of sub-properties is to indicate their "liveness," whether the server
> is
> enforcing the syntax and semantics of the property.
> 
> This draft introduces two main innovations: a tree data model for
> properties, and a property naming mechanism for combining the URI of a
> resource and the URI for a property type into a single URI which
> identifies
> an instance of that property on the resource. The tree data model
> provides
> support for sub-properties, which then afford typing support and
> internationalization support. The property naming mechanism allows
> existing
> HTTP/1.1 methods (GET, DELETE, PUT) to be used for operations on
> properties,
> thus reducing the number of new methods and helping to ensure the
> utility of
> methods as a mechanism for caching and security.
> 
> 2 A Property Model for HTTP Resources
> 
> 2.1 Overview
> 
> A property consists of a name and a value. However it is often the
> case that
> a property may itself contain properties, such as a sub-property which
> specifies its parent property is read only. The combination of
> properties
> and sub-properties creates a tree.
> 
>   Resource Root Property
>             |
>          Property
>         /       \
>   Read Only      (Some Value)
>        |
>     Yes/No
> 
> 2.2 Property Tree
> 
> The properties defined on a resource create a tree structure, whose
> root
> node is called the root property. The property tree consists of two
> types of
> nodes, a property node and a value node. A property node may have any
> number
> of children, those children may in turn consist of any number and any
> combination of property and values nodes. The ordering of these
> children
> must be maintained. Value nodes do not have any children as they can
> not
> contain properties, only a value. Property nodes are named, value
> nodes are
> referred to via their parent.
> 
> To conceptualize this property model, one builds the previously
> mentioned
> tree. Internal nodes are property nodes and leaf nodes are value
> nodes.
> 
> 2.3 Multivalued Properties
> 
> It is possible for the children of a property to contain several
> properties
> that have the same name. In order to prevent confusion among
> identically
> named siblings, the ordering of siblings MUST be maintained by the
> resource.
> Thus it is now possible to differentiate siblings through the use of
> an
> index.
> 
> 2.4 Property Names
> 
> A property name identifies both the syntax and semantics of the
> children of
> a property node. It is critical that property names do not collide,
> that is,
> two principals defining the same property name with two different
> meanings.
> 
> The URI framework provides for a mechanism to prevent namespace
> collision
> and for varying degrees of administrative control. Rather than
> reinvent
> these desirable features, DAV properties make use of them by requiring
> that
> all DAV property names MUST be URIs.
> 
> 2.5 Schemas
> 
> A schema is a group of property names. A schema may also define
> relationships between properties. It is often useful to indicate
> support for
> a particular schema in a request or a response. Schema discovery is
> also
> useful for determining if a system supports a group of properties. A
> property does not necessarily contain sufficient information to
> identify any
> schemas it may be a member of.
> 
> As with property names, schemas MUST use URIs as their names.
> 
> 2.6 Property Morphing
> 
> 2.6.1 Problem Definition
> 
> Property definitions change in two ways, either a new property is
> added or
> the value is marked up with new information.
> 
> An example of the first class of change will soon be upon us. The
> Digital
> Signature (DSIG) group at the W3C
> <http://www.w3.org/Security/DSig/Overview.html> is currently working
> on a
> mechanism for signing chunks of data and properties. A value that
> previously
> consisted of only a string will be turned into a property containing a
> signature property and the string value. What would an older client,
> written
> before DSIG, do? Where once it looked only for a string, now it finds
> a
> string and a property.
> 
> An example of the second class of change, markup can turn unstructured
> data
> into structured data. For example, a string which once contained a
> name is
> instead turned into two properties, one indicating the personal name
> and the
> second indicating the family name. What would an older client, written
> before the marked up format, do? Where once the client looked only for
> a
> string, now it finds two properties.
> 
> 2.6.2 Solution Requirements
> 
> A mechanism must be provided so that a client can examine the children
> of a
> property and upon encountering unknown properties know to either
> ignore the
> unknown property or to ignore the markup and promote the property's
> children
> one level up the parse tree.
> 
> 2.7 Visualizing a Property Tree Using XML
> 
> While it is possible to visualize tree structures in many ways, for
> use by
> WebDAV, this specification defines a linear visualization of property
> trees
> using the Extensible Markup Language (XML) [Bray, 1997] suitable for
> transmission as part of an HTTP protocol stream.
> 
> A sketch of an algorithm for creating an XML linearization of a
> property
> tree is given below.
> 
> Begin by printing an "<XML>" element, if this is a standalone
> document.
> 
> Next, perform a traversal of the property tree, collecting the set of
> all
> schemas used by all properties. Print one "<XML:Namespace>" ... "<AS>"
> XML
> entity pair for each schema in use, ensuring that unique tags are used
> in
> the "<AS>" XML entities. Save the mapping between schema names.
> 
> Next, perform a preorder traversal of the tree. For each node, print
> its
> name as "<"{unique schema tag}":"{property URI which is relative to
> the
> schema's URI}">", then print its value, then print "</>". Note that
> the
> process is recursive for values which contain properties. Whitespace
> may be
> printed between XML entities for prettyprinting.
> 
> Print a closing "</>" (to close the "<XML>") if the document is
> standalone.
> 
> A detailed description of "<XML:Namespace>" and "<AS>" XML entities is
> given
> in Appendix 4.
> 
> 3 Property Identifiers
> 
> 3.1 Problem Definition
> 
> The addition of properties to the HTTP object model result in the
> state of
> HTTP resources containing two separate areas, the body of the resource
> and
> the properties of the resource. A mechanism is needed to unambiguously
> refer
> to both.
> 
> 3.2 Solution Requirement
> 
> The mechanism used for referring to the resource directly must also be
> usable for referring to the resource's properties in such a manner
> that even
> non-DAV aware clients can retrieve DAV properties.
> 
> 3.3 DAV URL Parameter
> 
> To allow for the specification of property information in the context
> of an
> http scheme URL, a switch is needed. This switch indicates that the
> path
> segments following it specify a property location. To this end the
> "DAV"
> param is introduced for use with http scheme URLs. All path segments
> to the
> right of the DAV param MUST be formatted according to the XML Link
> standard,
> described in appendix 3, XML Linking.
> 
> 3.4 Hierarchical Naming
> 
> Properties on a resource are referred to as a hierarchy from the root
> property on down. Thus if a resource has an author property defined on
> its
> root property, which itself contains a family name property, then a
> hierarchy three levels deep is needed to refer directly to the family
> name
> property.
> 
> Root Property - Author Property - Family Name Property
> 
> The Root property is defined as "/". However both the author and
> family name
> properties are referred to using URIs. The XML Link standard provides
> a
> mechanism to refer to nested URIs.
> 
> For example, the following properties are defined on
> http://somewhere.com/resource.
> 
> <XML>
>  <Namespace><Ref>http://www.w3.org/standards/z39.50/</><AS>Z</></>
>  <Namespace><Ref>AIIM:Dublin:</><AS>D</>
>  <Z:Author><D:PersonalName>Shirley</><D:FamilyName>Mansai</></>
> </>
> 
> To create a reference to the value "Mansai" one would perform the
> following
> steps.
> 
>   1. Add the DAV parameter to the base URI,
>      http://somewhere.com/resource;DAV.
>   2. Add "/" to refer to the root of the resource's property
> namespace,
>      http://somewhere.com/resource;DAV/.
>   3. Change the author attribute's name into parameter format by
> changing
>      the "/" to "!" and encasing it in parenthesis. We must encase it
> in
>      parenthesis in order to indicate that we have made the "/" to "!"
>      translation. We make the translation in order to prevent
> confusion over
>      where segments are and to make sure that relative URIs will
> continue to
>      work.
> 
> http://somewhere.com/resource;DAV/(http:!!www.w3.org!standards!z39.50!
> author).
>   4. Next we continue the path by adding the family name attribute.
> Because
>      it does not include any "/" it does not require encoding.
> 
> http://somewhere.com/resource;DAV/(http:!!www.w3.org!standards!z39.50!
> author)/AIIM:Dublin:FamilyName.
> 
> The process is now complete, the URL can be used in a GET or PATCH to
> retrieve or alter the value. See appendix 3 for more information.
> 
> 3.5 Compatibility with legacy systems
> 
> 3.5.1 Problem Definition
> 
> The HTTP parameter space is uncontrolled, thus someone may already be
> using
> a parameter with a value of "DAV" for some end other than the one
> described
> here. Thus a client sending a URI with a DAV param to a server may
> receive
> an unexpected or inappropriate response.
> 
> 3.5.2 Solution Requirement
> 
> A mechanism is needed to prevent namespace collisions.
> 
> 3.5.3 Proposed Solution
> 
> All DAV compliant servers MUST honor the DAV param type on http URLs.
> Thus
> if a client knows it is talking to a DAV server, it can safely send an
> http
> URL with the DAV param.
> 
> The client may send the http URL with the DAV param extension to a
> server
> that is not know to be DAV compliant if the client uses PEP [Connolly,
> 1997]
> to prevent collisions. The proper PEP header is:
> 
> DAVPEP = "PEP: {{map "DAV"}{strength must}}"
> 
> Note that this header PEP header is not compliant with [Connolly,
> 1997] but
> the author has spoken with the authors of the PEP draft and they will
> be
> changing the format to make the example legal.
> 
> 4 DAV Schema
> 
> The DAV Schema is specified as http://www.ietf.org/standards/dav/.
> This
> schema is used to indicate support for properties that can be defined
> on a
> resource and XML entities that can be returned in responses.
> 
> 4.1 Properties
> 
> 4.1.1 Live Property
> 
> Name: http://www.ietf.org/standards/dav/live
> Purpose: To indicate that the parent property has its syntax and
> semantics
> enforced by the resource on which it is recorded.
> Schema: http://www.ietf.org/standards/dav/
> Parent: Any property
> Values: None
> Description: This property is used exclusively in a response to
> indicate if
> the resource a property is recorded on is enforcing the syntax and
> semantics
> of the property. The absence of the Live property tells the client
> that the
> corresponding property does not have its syntax and semantics enforced
> by
> the resource on which it is recorded.
> 
> 4.1.2 ReadOnly Property
> 
> Name: http://www.ietf.org/standards/dav/readonly
> Purpose: To indicate that the parent property can only be retrieved,
> not set
> through the property mechanism.
> Schema: http://www.ietf.org/standards/dav/
> Parent: Any property
> Values: None
> Description: This property is used to indicate that the parent
> property can
> only be retrieved, not set through the property mechanism. This
> property is
> not meant as an access control mechanism but rather to reflect the
> fact that
> the property is not designed to have its value set through the
> property
> mechanism.
> 
> 5 Link Property
> 
> 5.1 Problem Description
> 
> A mechanism is needed to associate resources with other resources.
> These
> associations, also known as links, consist of three values, a type
> describing the nature of the association, the source of the link, and
> the
> destination of the link. In the case of annotation, the source and
> destination of a link may not be the resource upon which the link is
> recorded.
> 
> 5.2 Solution Requirements
> 
> The association mechanism must make use of the property mechanism in
> order
> to make the existence of the associations searchable.
> 
> 5.3 Link Property
> 
> Name: http://www.ietf.org/standards/dav/link
> Purpose: To indicate the existence of a link associated with the
> parent
> property.
> Schema: http://www.ietf.org/standards/dav/
> Parent: Any property that needs to have a link associated with it.
> Values: Src 1*Dst
> Description: Link is used to provide the source and one or more
> destinations
> of the link. The parent property provides the type. Link is a
> multivalued
> property so multiple Links may be used together to indicate multiple
> links
> with the same type.
> 
> 5.4 Src Property
> 
> Name: http://www.ietf.org/standards/dav/src
> Purpose: To indicate the source of a link.
> Schema: http://www.ietf.org/standards/dav/
> Parent: http://www.ietf.org/standards/dav/link
> Values: URI
> 
> 5.5 Dst Property
> 
> Name: http://www.ietf.org/standards/dav/Dst
> Purpose: To indicate one or more destinations of a link
> Schema: http://www.ietf.org/standards/dav/
> Parent: http://www.ietf.org/standards/dav/link Values: URI
> 
> 5.6 Example
> 
> <XML>
> 
> <Namespace><Ref>http://www.ietf.org/standards/dav/</><AS>D</></>
>         <Namespace><Ref>http://www.foocorp.com/Project/</><AS>F</></>
>         <D:Source>
>                 <D:Link>
>                         <F:ProjectFiles>Source</>
>                         <src>http://foo.bar/program</>
>                         <dst>http://foo.bar/source/main.c</>
>                 </>
> 
>                 <D:Link>
>                         <F:ProjectFiles>Library</>
>                         <src>http://foo.bar/program</>
>                         <dst>http://foo.bar/source/main.lib</>
>                 </>
> 
>                 <D:Link>
>                         <F:ProjectFiles>Makefile</>
>                         <src>http://foo.bar/program</>
>                         <dst>http://foo.bar/source/makefile</>
>                 </>
>         </>
> </>
> 
> In this example the resource http://foo.bar/program has a source
> property
> defined on it which contains three links. Each link contains three
> properties, two of which, src and dst, are part of the DAV schema,
> defined
> in this document, and one which is defined by the schema
> http://www.foocorp.com/project/ (Source, Library, and Makefile). A
> client
> which only implements the properties in the DAV spec will not know
> what the
> foocorp properties are and will ignore them, thus seeing the expected
> source
> and destination links. However an enhanced client may know about the
> foocorp
> properties and thus be able to present the user with additional
> information
> about the links.
> 
> 6 Properties and Methods
> 
> 6.1 DELETE
> 
> The delete method, when used on a property, causes the property and
> its
> children to be removed.
> 
> 6.2 GET
> 
> A GET on a property returns the name of the property and its children.
> Accept types may be used to specify the format of the return value but
> all
> DAV compliant servers MUST at minimum support a return type of
> application/XML. If application/XML is used as the response format
> then it
> MUST include the http://www.ietf.org/standards/dav/ schema.
> 
> 6.2.1 GetResult XML Entity
> 
> Name: http://www.ietf.org/standards/dav/getresult
> Purpose: To contain the results of a GET request
> Schema: http://www.ietf.org/standards/dav/
> Parent: Any, usually <XML>
> Values: An XML Entity
> Description: The GetResult XML Entity provides the context to inform
> the
> client that its contents are not just some XML entity, but an XML
> representation of the requested property.
> 
> 6.2.2 Example
> 
> GET bar;DAV/(http:!!www.w3.org!standards!z39.50!Authors) HTTP/1.1
> Host: foo.com
> 
> HTTP/1.1 200 OK
> Content-Type: application/xml
> Content-Length: xxxx
> E-tag: "1234"
> Last-Modified: xxxx
> 
> <XML>
> 
> <XML:Namespace><Ref>http://www.ietf.org/standards/dav/</><AS>D</></>
> 
> <XML:Namespace><Ref>http://www.w3.com/standards/z39.50/</><AS>Z</></>
>         <D:GetResult><Z:Authors>
>                         <Author>Jane Doe</>
>                         <Author>Joe Doe</>
>                         <Author>Lots o'Doe</>
> </>     </>     </>
> 
> 6.3 PATCH Method
> 
> The PATCH method, in the most general sense, specifies how to alter a
> resource. The message body controls the actual action taken by a
> PATCH. All
> DAV compliant servers are required to support the use of the
> application/XML
> content-type using the http://www.ietf.org/standards/dav/patch/ schema
> in a
> PATCH method with a request-URI that points to a property.
> 
> The changes in a http://www.ietf.org/standards/dav/patch/ request MUST
> be
> atomically executed, partial results are not allowed.
> 
> 6.3.1 Request URI
> 
> The request URI of a PATCH method with the
> http://www.ietf.org/standards/dav/patch/ schema MUST point to the root
> of
> the resource's properties.
> 
> 6.3.2 PropertyUpdate XML Entity
> 
> Name: http://www.ietf.org/standards/dav/patch/PropertyUpdate
> Purpose: To contain a request to alter the properties on a resource.
> Schema: http://www.ietf.org/standards/dav/patch/
> Parent: <XML>
> Value: *(Create | Remove | Insert)
> Description: This XML entity is a container for the information
> required to
> modify the properties on the resource. This XML Entity is multivalued.
> 
> 6.3.3 Create XML Entity
> 
> Name: http://www.ietf.org/standards/dav/patch/create
> Purpose: To create the DAV property specified inside the Create XML
> entity.
> Schema: http://www.ietf.org/standards/dav/patch/
> Parent: http://www.ietf.org/standards/dav/patch/PropertyUpdate Values:
> XML:Ref PatchValue
> Description: This XML entity contains two values, a Ref and a
> PatchValue.
> The Ref contains the name of the property to be created or
> overwritten, this
> URI in Ref MUST be a relative URI whose base is the request-URI. The
> PatchValue XML entity contains the value the new property is to have,
> this
> value can contain both property and value nodes.
> 
> 6.3.4 Remove XML Entity
> 
> Name: http://www.ietf.org/standards/dav/patch/remove
> Purpose: To remove the DAV property specified inside the Remove XML
> entity.
> Schema: http://www.ietf.org/standards/dav/patch/
> Parent: http://www.ietf.org/standards/dav/patch/PropertyUpdate Values:
> XML:Ref
> Description: Remove orders that the property specified in Ref and its
> children removed. Ordering the removal of a property that does not
> exist is
> not an error. The URI in Ref MUST be a relative URI whose base is the
> request-URI.
> 
> 6.3.5 Insert XML Entity
> 
> Name: http://www.ietf.org/standards/dav/patch/insert
> Purpose: To insert a DAV property between other DAV properties of the
> same
> name.
> Schema: http://www.ietf.org/standards/dav/patch/
> Parent: http://www.ietf.org/standards/dav/patch/PropertyUpdate
> Values: InsertPoint InsertName PatchValue
> Description: Insert is used to insert the property referred to in
> InsertName, whose value is given in PatchValue, at the position held
> by the
> value specified in InsertPoint.
> 
> [Author's Note - Currently there is no way to directly address a
> value. So
> if I have the equivalent of <foo>bar<blah></>oops</> there is no way
> for me
> to say "I want "oops" to become "correct"". I have to replace the
> entire foo
> property.]
> 
> 6.3.6 InsertPoint XML Entity
> 
> Name: http://www.ietf.org/standards/dav/patch/InsertPoint
> Purpose: To specify a property that the new property should either be
> inserted before or after.
> Schema: http://www.ietf.org/standards/dav/patch/
> Parent: http://www.ietf.org/standards/dav/patch/Insert
> Values: Position Ref
> Description: The value in the Ref MUST be a relative URI whose base is
> the
> request-URI.
> 
> 6.3.7 Position XML Entity
> 
> Name: http://www.ietf.org/standards/dav/patch/position
> Purpose: To specify if the property to be inserted is to be inserted
> before
> or after the property specified in InsertPoint.
> Schema: http://www.ietf.org/standards/dav/patch/
> Parent: http://www.ietf.org/standards/dav/patch/InsertPoint
> Values: "Before" | "After"
> Description: If the value is Before then the property specified in
> InsertName is to be inserted in the position directly before the
> position
> held by the property specified in InsertPoint. If the value is After
> then
> the property specified in InsertName is to be inserted in the position
> after
> the position held by the property specified in InsertPoint.
> 
> 6.3.8 InsertName XML Entity
> 
> Name: http://www.ietf.org/standards/dav/patch/position
> Purpose: To specify the name of the new property to be inserted
> Schema: http://www.ietf.org/standards/dav/patch/
> Parent: http://www.ietf.org/standards/dav/patch/Insert
> Values: Ref
> Description: The Ref's value is the name of the property to be created
> at
> the position specified by InsertPoint. The URI MUST be relative and
> its base
> MUST be the request-URI. The value MUST NOT have an index on it.
> 
> 6.3.9 PatchValue XML Entity
> 
> Name: http://www.ietf.org/standards/dav/patch/patchvalue
> Purpose: To specify the name and when appropriate the value, of the
> particular property to be altered.
> Schema: http://www.ietf.org/standards/dav/patch/
> Parent: Any parent which needs to specify the contents of a property
> Values: The contents of a property
> 
> 6.3.10 Response Codes
> 
> 200 OK - The command succeeded. As there can be a mixture of PUT and
> DELETEs
> in a body, a 201 Create seems inappropriate.
> 
> 400 Bad Request - The client has provide a value whose syntax is
> illegal for
> the property.
> 
> 401 Unauthorized - The client does not have authorization to alter one
> of
> the properties. This error also occurs if a property is inherently
> read
> only.
> 
> 403 Forbidden - The client, for reasons the server chooses not to
> specify,
> can not alter one of the properties.
> 
> 405 Conflict - The client has provided a value whose semantics are not
> appropriate for the property.
> 
> 6.3.11 Example
> 
> PATCH bar;DAV/ HTTP/1.1
> Host: www.foo.com
> Content-Type: application/XML
> Content-Length: xxxx
> 
> <XML>
> 
> <XML:Namespace><Ref>http://www.ietf.org/standards/dav/patch/</><AS>P</
> ></>
>         <XML:Namespace><Ref>D:patch/</><AS>P</></>
> 
> <XML:Namespace><Ref>http://www.w3.com/standards/z39.50/</><AS>Z</></>
> 
> <XML:Namespace><Ref>http://www.w3.com/standards/dublin/</><AS>D</></>
>         <P:PropertyUpdate>
>                 <Create>
>                         <XML:Ref>Z:authors</>
>                         <PatchValue>
>                                 <Author>Jim Whitehead</>
>                                 <Author>Roy Fielding</>
>                         </>
>                 </>
> 
>                 <Remove><Ref>D:Copyright-Onwer</></>
>                 <Insert>
> 
> <InsertPoint><Position>Before</><XML:Ref>Z:producer</></>
>                         <InsertName><XML:Ref>Z:Last-Modified</></>
>                         <PatchValue></>
>                 </>
>                 <Insert>
> 
> <InsertPoint><Position>After</><XML:Ref>Z:editor(1)</></>
>                         <InsertName><XML:Ref>Z:editor</></>
>                 </>
> </>     </>
> 
> 6.4 PUT
> 
> A PUT is specified in order to control what is returned by a GET.
> However a
> GET on a property always returns some sort of property containment
> format.
> As such PUT can not be used if the Request-URI refers to a property.
> 
> 6.5 SEARCH
> 
> [Author's Note: The search section has never had a very good
> specification
> and there has never been very wide agreement on what features should
> be made
> available. The search specified here is the authors best efforts to
> try and
> synthesize all the features and restrictions which have been asked for
> to
> date.]
> 
> 6.5.1 Request-URI
> 
> The request-URI of the search method specifies the scope of the
> search. If
> the request-URI does not contain the ";DAV/" switch then the scope of
> the
> search is all the properties on that resource. If the request-URI in
> the
> previous case is a collection then the scope of the search is extended
> to
> the collection's propagate members. If the request-URI specifies part
> of the
> property space then the search is restricted to only that property
> space on
> that resource, even if the resource is a container.
> 
> So, for example if http://www.foo.com/bar was the request-URI but not
> a
> container, the search would be across all of http://www.foo.com/bar's
> properties.
> 
> If was a container, then the search would be across all the properties
> on
> and all its propagate member's properties. However if the request-URI
> were
> http://bar/foo;DAV/ then the scope would only be the properties on
> http://bar/foo, not on any of its propagate members.
> 
> The Depth header MUST NOT be used on a SEARCH method.
> 
> 6.5.2 Command Format
> 
> The effects of a SEARCH method are defined by the message body. This
> section
> defines an application/xml content type using the
> http://www.ietf.org/standards/dav/search/ schema. This method is not
> normally cacheable.
> 
> 6.5.2.1 Limited-Search XML Entity
> 
> Name: http://www.ietf.org/standards/dav/search/limited-search
> Purpose: To specify the set of matching properties
> Schema: http://www.ietf.org/standards/dav/search/
> Parent: <XML>
> Values: The value is a single OR. The OR may only contain ANDs. The
> ANDs
> MUST contain NAME and VALUE properties.
> Description: This property indicates a very limited search. The search
> may
> only be on HTTP properties.
> 
> 6.5.2.2 OR XML Entity
> 
> Name: http://www.ietf.org/standards/dav/search/or
> Purpose: To take its members, evaluate them, get a true or false
> result,
> "or" the results together, and have that be the total result.
> Schema: http://www.ietf.org/standards/dav/search/
> Parent: Any property where an OR makes sense
> Values: Any properties that can be evaluated into a true or false
> value. One
> or more properties may be included.
> 
> 6.5.2.3 AND XML Entity
> 
> Name: http://www.ietf.org/standards/dav/search/and
> Purpose: To take its members, evaluate them, get a true or false
> result,
> "and" the results together, and have that be the total result.
> Schema: http://www.ietf.org/standards/dav/search/
> Parent: Any property where an AND makes sense
> Values: Any properties that can be evaluated into a true or false
> value. One
> or more properties may be included.
> 
> 6.5.2.4 Name XML Entity
> 
> Name: http://www.ietf.org/standards/dav/search/name
> Purpose: To provide a pattern against which property names are to be
> compared. If the name matches then the property evaluates to true,
> otherwise
> false.
> Schema: http://www.ietf.org/standards/dav/search/
> Parent: Any property that is performing a search on a property.
> Values: Match-Stream
> 
> 6.5.2.5 Value XML Entity
> 
> Name: http://www.ietf.org/standards/dav/search/value
> Purpose: To provide a pattern against which property values are to be
> compared. If the value matches then the property evaluates to true,
> otherwise false.
> Schema: http://www.ietf.org/standards/dav/search/
> Parent: Any property that is performing a search on a property.
> Values: Match-Stream
> 
> 6.5.2.6 Match-String XML Entity
> 
> Name: http://www.ietf.org/standards/dav/search/match-string
> Purpose: To specify a search pattern to be matched against an octet
> stream
> Schema: http://www.ietf.org/standards/dav/search/
> Parent: Any property that needs to match a string against a search
> pattern
> Values: ("*" | "?" | EncodedOctet)
> EncodedOctet = <An EncodedOctet uses XML encoding to encode "*" and
> "?" as
> well as "<" and ">"
> Description: This entity provides a template against which anything
> that can
> be expressed as an octet stream may be compared. "*" is a wildcard
> that
> matches zero or more unspecified contiguous octets. "?" is a wildcard
> that
> matches exactly one unspecified octet.
> 
> 6.5.3 Response Format
> 
> The response is an application/xml message body which contains a
> single
> SearchResult XML entity whose contents are a series of XML entities
> representing matching properties.
> 
> 6.5.3.1 SearchResult XML Entity
> 
> Name: http://www.ietf.org/standards/dav/search/searchresult
> Purpose: To contain the results of a SEARCH request
> Schema: http://www.ietf.org/standards/dav/search/
> Parent: Any, usually <XML>
> Values: An XML Entity
> Description: The SearchResult XML Entity provides the context to
> inform the
> client that its contents are not just some XML entity, but an XML
> representation of the requested property.
> 
> 6.5.4 Example
> 
> SEARCH  /container/ HTTP/1.1
> Host: www.foo.bar
> Content-Length: xxxx
> Content-Type: application/xml
> 
> <XML>
> 
> <XML:Namespace><Ref>http://www.ietf.org/standards/dav/search/</><AS>S<
> /></>
>         <S:limited-search><OR><AND><Name>*</></></></>
> </>
> 
> HTTP/1.1 200 OK
> Content-Type: application/xml
> Content-Length: xxxxx
> 
> <XML>
>         <XML:Namespace><Ref>D:search/</>S</>
>         <XML:Namespace><Ref>http://www.foo.bar/container</><AS>R</></>
> 
> <XML:Namespace><Ref>http://www.aiis.org/standards/dav/</><AS>A</>
>         <S:SearchResult>
>                 <XML:Namespace><Ref>R:(A)</><AS>RA</></>
>                 <RA:author><D:live></>Jim Whitehead</>
>                 <XML:Namespace><Ref>R:/member1/(A)</><AS>M1</></>
>                 <M1:author><D:live></>Roy Fielding</>
> </>     </>
> 
> The result will return all properties on the container and its
> members. In
> this case only two properties were found, one on the container and one
> on
> one of its members, both properties are live.
> 
> 7 References
> 
> [Berners-Lee, 1997] T. Berners-Lee, "Metadata Architecture."
> Unpublished
> white paper, January 1997.
> http://www.w3.org/pub/WWW/DesignIssues/Metadata.html.
> 
> [Bray, 1997] T. Bray, C. M. Sperberg-McQueen, "Extensible Markup
> Language
> (XML): Part I. Syntax", WD-xml-lang.html,
> http://www.w3.org/pub/WWW/TR/WD-xml-lang.html.
> 
> [Connolly, 1997] D. Connolly, R. Khare, H.F. Nielsen, "PEP - an
> Extension
> Mechanism for HTTP", Internet draft, work-in-progress.
> draft-ietf-http-pep-03.txt,
> ftp://ds.internic.net/internet-drafts/draft-ietf-http-pep-03.txt.
> 
> [Lasher, Cohen, 1995] R. Lasher, D. Cohen, "A Format for Bibliographic
> Records," RFC 1807. Stanford, Myricom. June, 1995.
> 
> [Maloney, 1996] M. Maloney, "Hypertext Links in HTML." Internet draft
> (expired), work-in-progress, January, 1996.
> 
> [MARC, 1994] Network Development and MARC Standards, Office, ed. 1994.
> "USMARC Format for Bibliographic Data", 1994. Washington, DC:
> Cataloging
> Distribution Service, Library of Congress.
> 
> [Miller et.al., 1996] J. Miller, T. Krauskopf, P. Resnick, W. Treese,
> "PICS
> Label Distribution Label Syntax and Communication Protocols" Version
> 1.1,
> W3C Recommendation REC-PICS-labels-961031.
> http://www.w3.org/pub/WWW/TR/REC-PICS-labels-961031.html.
> 
> [WebDAV, 1997] WEBDAV Design Team. "A Proposal for Web Metadata
> Operations."
> Unpublished manuscript.
> http://www.ics.uci.edu/~ejw/authoring/proposals/metadata.html
> 
> [Weibel et al., 1995] S. Weibel, J. Godby, E. Miller, R. Daniel,
> "OCLC/NCSA
> Metadata Workshop Report."
> http://purl.oclc.org/metadata/dublin_core_report.
> 
> [Yergeau, 1997] F. Yergeau, "UTF-8, a transformation format of Unicode
> and
> ISO 10646", Internet Draft, work-in-progress,
> draft-yergeau-utf8-rev-00.txt,
> http://www.internic.net/internet-drafts/draft-yergeau-utf8-rev-00.txt.
> 
> 8 Appendix 1 - Content Type Application/XML
> 
> 8.1 Syntax
> 
> The application/XML content type contains an XML document. Its syntax
> is as
> defined below.
> 
> XML = XMLStart *XMLEntity Close
> 
> XMLStart = "<" "XML" ">"
> 
> XMLEntity= Open *(XMLText | XMLEntity) Close
> 
> Close = "</>" | "<""/"Entity-Name
> Markup">"
> 
> Open = "<" Entity-Name Markup ">"
> 
> XMLText = <An Octet Stream which uses XML encoding
> for "<" and ">">
> 
> Entity-Name = [As-Tag ":"] Name
> As-Tag = 1*Alpha
> 
> Name = (alpha | "_") *(alpha | digit |
> "." | "-" | "_" | other)
> 
> Other = <Other characters must be encoded>
> 
> Markup = SP "-" | ""
> 
> 8.2 XML Entity
> 
> An XML entity, as defined in the BNF, is an open tag with content
> followed
> by a close tag. In order to prevent confusion with the term entity as
> used
> in HTTP, the term XML entity will be used.
> 
> The first XML entity of a XML document MUST be the <XML> XML entity.
> This
> XML entity tells the parser that it is dealing with an XML document.
> So long
> as this XML entity is present the parser can be sure that it can parse
> the
> document, even if XML has been extended. If XML is ever altered in a
> manner
> that is not backwards compatible with this specification then the
> content-type and the outer most XML entity MUST be changed.
> 
> 8.3 Entity-Name
> 
> All XML entity names must map to URIs. However due to historical
> restrictions on what characters may appear in an XML entity name, URIs
> cannot be expressed in an XML entity name. This issue is dealt with in
> more
> detail in section 10.
> 
> Entity-Names without [AS] are relative URIs whose base is the
> enclosing
> Entity-Name. If the enclosing Entity-Name is <XML> then the
> Entity-Name MUST
> use an [AS].
> 
> 8.4 Close
> 
> The close production marks the end of a XML entity.
> 
> 8.5 XML Encoding
> 
> In different contexts certain characters are reserved, for example "/"
> can
> not be used in an XML entity name and ">"/"<" can not be used in a
> value. As
> such these values must be encoded as follows:
> 
> Encoding = Decimal | Hex4
> 
> Decimal = "&" Non-Zero *("0" | Non-Zero)
> 
> Hex4 = "&u-" 4(Hex)
> 
> Non-Zero = "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9"
> 
> Hex = "0" | Non-Zero | "A" | "B" | "C" | "D" | "E" | "F"
> 
> The numbers MUST map to the UTF8 character encodings. Please note that
> the
> "&" character must always be encoded.
> 
> 8.6 Markup Modifier
> 
> The markup modifier, ("-", after the end of an XML entity) instructs
> the
> principal how to treat a XML entity with an unknown name. If the
> modifier is
> used and the XML entity is not recognized then the XML entity name
> MUST be
> stripped and the XML entity's contents promoted one level in the parse
> tree.
> If the modifier is not used and the XML entity name is unknown then
> the XML
> entity and its contents MUST be ignored.
> 
> 8.7 XML Syntax Shorthand
> 
> The following template is recommended for efficiently providing a
> description of an XML entity.
> 
> Name: The name of the XML entity
> Purpose: A one line description of the XML entity's purpose.
> Schema: The schema, if any, that the XML entity belongs to
> Parent: XML entities that this XML entity may be a child of.
> Values: A description, usually a BNF, of the simple and compound
> values that
> the XML entity supports.
> Description: Further information.
> Example: An example of the XML entity's use.
> 
> 9 Appendix 2 - Parameter Syntax for Content-Type Application/XML
> 
> HTTP 1.1 provides for a mechanism to include a parameter with a
> content
> type. In order to prevent namespace collisions the parameters for
> application/XML must use the following syntax:
> 
> Parameter = #(<">URI<">  ["=" (token | Quoted-String)])
> 
> 9.1 Schema Content-Type Parameter
> 
> Parameter = <"> http://www.w3.org/standards/xml/content-type/schema/
> <"> "=" <"> #URI <">
> 
> The http://www.w3.org/standards/xml/content-type/schema/ URL is used
> as a
> parameter to an application/xml content type. The URL indicates that
> its
> value lists some subset of the schemas defined in NameSpace parameters
> within the enclosed document. The URI can also be used in requests to
> indicate schemas that should appear in the result.
> 
> An example of the use of this parameter is to include it in an
> accept-type
> header on a request to indicate that the response should contain the
> specified namespace. Thus the client is able to inform the server of
> its
> support for a particular set of namespaces. The server is not required
> to
> return a result with the specified namespaces.
> 
> 10 Appendix 3 - URI Path Encoding
> 
> 10.1 Problem Definition
> 
> A mechanism is needed to refer to specific DAV properties in a manner
> that
> can handle simple, composite, and multivalued DAV properties.
> 
> 10.2 Solution Requirement
> 
> The reference mechanism must use the standard URL syntax so it can be
> used
> with both currently existing and future URLs. For example, the syntax
> could
> be appended to an HTTP URL to specify a HTTP property on that URL.
> 
> 10.3 Path Component
> 
> URIPath = "/" [path-segments]
> 
> Path-segments = segment *("/" segment)
> 
> Segment = ("(" Abs-URI ")" | Rel-URI)[Index]*(";" param)
> 
> Index = ["(" ["-"]*digit ")"]
> 
> Abs-URI = < An absolute or relative URI which has been URI-Path
> encoded >
> 
> Rel-URI = < A relative URI for which URI-Encoding(Rel-URI) == Rel-URI
> >
> 
> URI-Path encoding consists of the following algorithm:
> 
>   1. URL encode all "!" characters
>   2. Map all "/" characters to "!" characters
> 
> Please note that all relative URIs are relative to the URI in the path
> segment preceding them. Hence the URI in the first path segment MUST
> be an
> absolute URI.
> 
> The purpose of the encoding is to allow URLs to be used as segments
> without
> having to use % encoding on all the "/" which produces a URL form
> which is
> extremely difficult for humans to deal with, and which changes the
> semantics
> of the URL.
> 
> 10.4 Composite DAV Properties
> 
> The DAV property namespace is hierarchical, allowing DAV properties to
> be
> nested within each other. In order to refer to a particular DAV
> property one
> must list all the DAV properties from the root to the desired DAV
> property.
> 
> For example, using XML notation for illustrative purposes,
> 
> <XML>
> 
> <XML:Namespace><Ref>http://www.aiim.org/standards/dublin/</><AS>A</></
> >
> 
> <XML:Namespace><Ref>http://www.ansi.org/standards/z39.50/</><AS>Z</></
> >
>         <A:author><Name>
>                         <Z:PersonalName >Freddie</>
>                         <Z:FamilyName >Mercury</>
> </>     </>     </>
> 
> Using the path specification one would refer to the PersonalName DAV
> property as
> "/(http:!!www.aiim.org!standards!dublin!author)/Name/(http:!!www.ansi.
> org!standards!z39.50!PersonalName)".
> Name does not have to be encased in parenthesis because it meets the
> rel-uri
> rule.
> 
> 10.5 Multivalued DAV Properties
> 
> A DAV property may often have several siblings, for example, the
> resource
> "A" has the following DAV properties defined on it, again using XML
> notation
> for illustrative purposes,
> 
> <XML>
>         <XML:Namespace><Ref>A</><AS>A</></>
>         <A:b>
>                 <c>e</>
>                 <d>f</>
>                 <c>g</>
>                 <d>h</>
> </>     </>
> 
> An index system is used to distinguish siblings with the same name.
> The
> index indicates the relative positions of multivalued sibling DAV
> properties
> to each other. The first sibling is at position 1 and the rest are at
> position N+1 where N is the position of the previous sibling. Negative
> position numbers may also be use such that -1 refers to the last
> sibling and
> the index is decremented for each subsequent sibling.
> 
> In cases where a multivalued DAV properties exists but no index is
> provided,
> the index value will default to 1.
> 
> Thus the parameters in the example would be referred to as follows:
>  Parameter               Negative
>  Value   Positive Index  Index
>  <a:b>
> 
>  <c>e</>
> 
>  <d>f</>
>          /A:b or /A:b(1)
>  <c>g</>
> 
>  <d>h</>
> 
>  </>
> 
>  <c>e</> /A:b/c or       /A:b/c(-2)
>          /A:b/c(1)
> 
>  <d>f</> /A:b/d or       /A:b/d(-2)
>          /A:b/d(1)
>  <c>g</> /A:b/c(2)       /A:b/c(-1)
>  <d>h</> /A:b/d(2)       /A:b/d(-1)
> 
> 11 Appendix 4 - XML URI
> 
> The "XML" scheme is to be registered with IANA as a reserved namespace
> that
> will be owned by the XML group through the W3C.
> 
> The new URI is defined as:
> 
> XML = "XML" ":" XML-Path
> 
> 12 Appendix 5 - XML Entities
> 
> 12.1 Ref XML entity
> 
> Name: XML:Ref
> Purpose: A XML entity that indicates that its contents are a URI.
> Schema: XML
> Parent: Any
> Value: URI
> 
> 12.2 Namespace
> 
> 12.2.1 Namespace XML entity
> 
> Name: XML:Namespace
> Purpose: To inform the parser that a particular schema is in use and
> to
> provide a shorthand name for referring to XML entities related to that
> schema.
> Schema: XML
> Parent: Any
> Value: (Ref [AS])
> 
> Description: This XML entity contains two XML entities, Ref and AS.
> The
> purpose of the XML entity is to inform the parser that a schema,
> identified
> by the value of the Ref XML entity, is in use and, when appropriate,
> to
> provide a shorthand name to refer XML entities derived from that
> schema
> using the AS XML entity. The AS mechanism is needed for efficiency
> reasons
> and because a URI can not be fully specified in an XML open tag. The
> Namespace XML entity's scope is all siblings and their children.
> 
> 12.2.2 AS XML entity
> 
> Name: XML:AS
> Purpose: To provide a short name for the URI of the schema provided in
> the
> Ref XML entity of a namespace XML entity.
> Schema: XML
> Parent: XML:Namespace
> Value: 1*Alpha
> 
> Description: The AS XML entity is used to provide a shorthand
> reference for
> the URI in the Ref XML entity of a Namespace XML entity. The value
> contained
> in the AS XML entity is generated at the XML producer's discretion,
> the only
> requirement is that all AS values MUST be unique within the contents
> of the
> parent of the namespace element.
> 
> All XML entity open tags contain a name of the form As-Tag:Name. The
> As-Tag
> is the value defined in an AS XML entity inside of a Namespace. To
> resolve
> the As-Tag:Name into a properly formatted URI replace "As-Tag:" with
> the URI
> provided in the Ref that the AS was defined with. Also note that AS
> value
> also applies to any URIs defined in a Ref inside of Namespace.
> 
> For example,
> 
> <XML>
>         <XML:Namespace><Ref>http://blah;DAV/</><AS>B</></>
>         <XML:Namespace><Ref>B:(B:)/</><AS>C</></>
>         <C:Moo></>
> </>
> 
> So B:(B:) translates to http://blah;DAV/(http:!!blah;DAV!)/ and C:Moo
> translates to http://blah;DAV/(http:!!blah;DAV!)/Moo.
> 
> 12.2.3 Required XML entity
> 
> Name: XML:Required
> Purpose: To indicate that the read MUST understand the associated
> Namespace
> in order to successfully process the XML document.
> Schema: XML
> Parent: XML:Namespace
> Value: None
> 
> 12.2.4 The XML URI and Namespace
> 
> In order to prevent a logical loop the XML namespace is said to be
> declared,
> with the AS value of "XML" as a consequence of the <XML> enclosing
> property.
Received on Monday, 16 June 1997 21:24:00 GMT

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