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Difference between revisions of "ContextId"

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== Introduction ==
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[[Image:Higgins_logo_76Wx100H.jpg|right]]
This page describes and defines a Higgins [[ContextId]].
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== Version ==
See also: [[Context Discovery]] and [[Context Discovery Components]].
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This page describes the concept of a [[ContextId]] as used in [[Context Data Model 2.0]].
  
 
== Definition ==
 
== Definition ==
A '''ContextId''' is a URI or XRI that identifies one [[Context]].
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* An identifier of a [[Context]]  
* A [[ContextId]] MUST conform to the ABNF defined below.
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* A ''Context UDI'' as defined in [http://www.azigo.com/udi/udi-syntax.html UDI Syntax]
* A [[ContextId]] must directly or indirectly (e.g. by resolution) provide sufficient information to both identify and open a [[Context]]. See the ''Context Discovery with a ContextId'' heading below.
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* Two different [[ContextId]]s may refer to the same [[Context]].
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* If two [[ContextId]]s are equal, they refer to the same underlying [[Context]] dataset, although not necessarily the same [[Context]] "container" instance. This means that, as a requester of information, different [[Digital Identity|Digital Identities]] may see different subsets of the [[Context]] based on the authorization passed in during authentication. A given [[ContextId]] may be used against multiple [[Context Provider]]s to produce the same [[Context]] (although, as mentioned, different [[Context]] instances).
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* The [[Identity Attribute Service (IdAS)]] can be used as a service to access a [[Context]] given a [[ContextId]]
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== Syntax ==
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[[Category:Context Data Model 2.0]]
The following [http://en.wikipedia.org/wiki/Augmented_Backus-Naur_form ABNF] defines a Higgins [[ContextId]]. Rules not defined in this ABNF are defined in the [http://wiki.oasis-open.org/xri/XriCd02/Xri2dot0Abnf ABNF for XRI 2.0] (which includes the IRI ABNF from [http://www.ietf.org/rfc/rfc3987.txt RFC 3987]).
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contextId          = contextURI / contextXRI
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contextURI        = contextfileURI / contexthttpURI
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contextfileURI    = [ "file://" ] ipath-abempty descriptor-ext
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descriptor-ext    = ".xrds" / ".xdi"                                                            ;see note 1
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contexthttpURI    = ( "http://" / "https://" ) iauthority
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                      ipath-abempty [ descriptor-ext ] [ "?" iquery ]
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contextXRI        = [ "xri://" ] contextQXRI /                                                  ;see note 2
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                      contextHXRI                                                                ;see note 3
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contextQXRI        = xri-authority [ "/($context) [ "*" / "!" ] / "/$context" ) [ xri-segment ] ] ;see note 4
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contextHXRI        = proxy-resolver "/" contextQXRI
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proxy-resolver    = ( "http://" / "https://" ) proxy-reg-name
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proxy-reg-name    = "xri." ireg-name
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Notes:
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# ".xrds" and ".xdi" are formats designed expressly for discovery and description of resources using HTTP(S) URIs and/or XRIs. XRDS format is defined by [http://www.oasis-open.org/committees/download.php/24286/xri-resolution-v2.0-wd-11-ed-02.doc XRI Resolution Working 2.0]. XDI format is being defined by the [http://www.oasis-open.org/committees/xdi OASIS XDI Technical Committee]. Other resource description file types can be supported by extending this ABNF rule.
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# QXRI (Query XRI) is an XRI in URI-normal form without the "xri://" prefix. See [http://docs.oasis-open.org/xri/2.0/specs/cd02/xri-resolution-V2.0-cd-02.pdf XRI Resolution 2.0].
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# HXRI (HTTP(S) XRI) is the format for encapsulating an XRI within an HTTP(S) URI for purposes of resolution by an XRI proxy resolver. See section 6 of [XRI Resolution 2.0 Committee Draft 02 XRI Resolution 2.0].
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# The two different forms of QXRI path shown here -- '''/($context)''' and '''/$context''' -- are to accommodate both [http://wiki.oasis-open.org/xri/XriCd02/Xri2dot0Abnf XRI 2.0 syntax] and the [http://wiki.oasis-open.org/xri/XriThree/SyntaxAbnf simplified syntax proposed for XRI 3.0].
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== Examples ==
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=== ContextURI ===
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A ContextId in ContextURI form can be either a file or HTTP(S) URI. In either case it must end with either ".xrds" or ".xdi".
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file://system/config/higgins.xrds
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file://system/config/higgins.xdi
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http://example.com/higgins/ldap.xrds
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https://example.com/higgins/ldap.xdi
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=== ContextQXRI ===
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A ContextQXRI (Query XRI) is a pure XRI in XRI-normal form that does not include the "xri://" prefix.
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=drummond/
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=drummond/$context$openid
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=drummond/$context$ldap
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=!F83.62B1.44F.2813/
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=!F83.62B1.44F.2813/$context$openid
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=!F83.62B1.44F.2813/$context+$ldap
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=drummond*mom/
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=drummond*mom/$context$openid
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=drummond*mom/$context$ldap
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@example/
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@example/$context$openid
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@example/$context$ldap
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@free*example/
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@free*example/$context$openid
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@free*example/$context$ldap
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=== ContextHXRI ===
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A contextHXRI is a ContextQXRI that uses an HXRI proxy resolver prefix. "xri.net" is a public HXRI proxy resolver operated by XDI.org. All others are examples.
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http://xri.net/=drummond/
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https://xri.net/=drummond/$context$openid
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http://xri.example.com/@example/$context$openid
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https://xri.example.org/@1000.a1b2.c3d4.9999/$context$ldap
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== Context Discovery using a ContextId ==
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A key property of a [[ContextId]] is that it can be resolved into the metadata necessary open a [[Context]]. Following are the discovery rules for each form of ContextId.
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=== ContextURI Discovery ===
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Note that since URIs do not share the same structured identifier characteristics as XRIs, they must resolve directly to an XRDS or XDI document containing the necessary Higgins context configuration metadata as described in this section.
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==== ContextfileURI ====
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# Open the identified file.
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# For an XRDS file, select the highest priority service endpoint that conforms to the [[Higgins XRDS Service Endpoint]] requirements.
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# For an XDI X3 file, parse the Higgins context configuration metadata from the X3 document as described in [[Higgins XDI Context Reference]].
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==== ContexthttpURI ====
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# Resolve the URI to a discovery document as specified in Section 6 of [http://docs.oasis-open.org/xri/2.0/specs/cd02/xri-resolution-V2.0-cd-02.pdf XRI Resolution 2.0] using EITHER OR BOTH of the following MIME types (depending on the client's preferred format and the server's available options):
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## '''application/xrds+xml''' for an XRDS document.
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## '''text/x3''' for an XDI X3 document.
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# If the MIME type of the discovery document is '''application/xrds+xml''', select the highest priority service endpoint that conforms to the [[Higgins XRDS Service Endpoint]] requirements.
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# If the MIME type is '''text/x3''', parse the Higgins context configuration metadata from the X3 document as described in [[Higgins XDI Context Reference]].
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=== ContextXRI Discovery ===
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==== Using XRDS ====
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# Resolve the authority component of the XRI as specified in [http://docs.oasis-open.org/xri/2.0/specs/cd02/xri-resolution-V2.0-cd-02.pdf XRI Resolution 2.0]. Trusted resolution is RECOMMENDED.
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# From this XRDS document, select the Higgins service endpoint as defined in Section 13 of [http://docs.oasis-open.org/xri/2.0/specs/cd02/xri-resolution-V2.0-cd-02.pdf XRI Resolution 2.0]. Note that this provides multiple options for ContextXRI authors to control service endpoint selection. Using the path component of the XRI to match a [[Higgins XRDS Service Endpoint]] is RECOMMENDED.
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# Parse the Higgins context metadata as defined in [[Higgins XRDS Service Endpoint]].
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==== Using XDI ====
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# Resolution of the authority component of the XRI may use either XRDS resolution or XDI context discovery.
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## For XRDS resolution, follow the same steps as described above, except that in the final XRDS document, the highest priority SEP of type '''xri://$xdi''' MUST be selected, and an XDI X3 document MUST be requested from that service endpoint URI.
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## For XDI context discovery, resolve the authority component of the XRI as specified in the XDI Contexts section of [http://wiki.oasis-open.org/xdi/XdiRdfModel XDI RDF Model]] document.
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# In both cases, from the final XDI document, parse the XDI context description as defined in [[Higgins XDI Context Reference]].
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== Relationship to OpenID ==
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Note that any ContextURI may be an OpenID identifier as defined by [http://openid.net/specs/openid-authentication-2_0.html OpenID Authentication 2.0].
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* ''Give examples of OpenID-based ContextIds here...''
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== Open Issues ==
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# Should the contextId ABNF support IRI (Internationalized Resource Identifiers) and not just URIs? Note that the ABNF above uses IRI rules; this needs to be changed if only URIs will be supported.
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== See Also ==
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* [[SubjectId]]
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* [[Relation]]
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* [[Higgins XRDS Service Endpoint]]
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* [[Concepts]]
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== Links ==
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* [http://eclipse.org/higgins Higgins Home]
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Latest revision as of 10:35, 31 May 2021

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Version

This page describes the concept of a ContextId as used in Context Data Model 2.0.

Definition

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