Difference between revisions of "ContextId"

Revision as of 23:12, 18 July 2007

Introduction

This page describes and defines a Higgins ContextId.

Definition

• A ContextId is a URI or XRI that identifies one Context.
• A ContextId MUST conform to the ABNF defined below.
• ContextIds either directly or indirectly (e.g. by resolution) provide sufficient information to identify a Context.
• Two different ContextIds may refer to the same Context.
• If two ContextIds are equal, they refer to the same underlying Context dataset, although not necessarily the same Context "container" instance, and, based on the authorization of the Digital Identity passed in during authentication, may only be permitted to see a subset of its contents.
• A given ContextId may be used against multiple Context Factorys to produce the same Context (although, as mentioned, different Context instances).
• ContextIds are used by the Identity Attribute Service (IdAS) API

ABNF

Note that this ABNF also defines a Higgins SubjectID and CSID (Contextualized SubjectID).

Rules not defined in this ABNF are defined in the ABNF for XRI 2.0 (which includes the IRI ABNF from RFC 3987.

contextId         = contextURI /
                    contextXRI
contextURI        = contextfileURI /
                    contexthttpURI
contextfileURI    = [ "file://" ] ipath-abempty descriptor-ext
descriptor-ext    = ".xrds" / ".xdi"                      ;see note 1
contexthttpURI    = ( "http://" / "https://" ) iauthority
                    ipath-abempty [ descriptor-ext ] [ "?" iquery ]
contextXRI        = [ "xri://" ] contextQXRI /            ;see note 2
                    contextHXRI                           ;see note 3
contextQXRI       = xri-authority / [ xri-segment ]
contextHXRI       = proxy-resolver "/" contextQXRI
proxy-resolver    = ( "http://" / "https://" ) proxy-reg-name
proxy-reg-name    = "xri." ireg-name
subjectID         = ifragment / xri-segment
csid              = csidURI /
                    csidXRI
csidURI           = contextURI "#" ifragment
csidXRI           = contextXRI "/" xri-segment

Notes:

1. These are the first two file types are designed expressly for discovery and description of resources using HTTP(S) URIs and/or XRIs. XRDS format is defined by XRI Resolution Working 2.0. XDI format is being defined by the OASIS XDI Technical Committee. Future file types can be supported by extending this ABNF rule.
2. QXRI (Query XRI) is an XRI in URI-normal form without the "xri://" prefix. See XRI Resolution 2.0.
3. 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 8 of XRI Resolution 2.0.

Examples

ContextURI

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".

file://system/config/higgins.xrds
file://system/config/higgins.xdi
http://example.com/higgins/ldap.xrds
https://example.com/higgins/ldap.xdi

ContextQXRI

A ContextQXRI (Query XRI) is a pure XRI in XRI-normal form that does not include the "xri://" prefix.

=drummond/
=drummond/$context+openid
=drummond/$context+ldap
=!F83.62B1.44F.2813/
=!F83.62B1.44F.2813/$context+openid
=!F83.62B1.44F.2813/$context+ldap
=drummond*mom/
=drummond*mom/$context+openid
=drummond*mom/$context+ldap
@example/
@example/$context+openid
@example/$context+ldap
@free*example/
@free*example/$context+openid
@free*example/$context+ldap

ContextHXRI

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.

http://xri.net/=drummond/
https://xri.net/=drummond/$context+openid
http://xri.example.com/@example/$context+openid
https://xri.example.org/@1000.a1b2.c3d4.9999/$context+ldap

Open Issues

1. 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.
2. Do we need a method in IdAS to test that two given ContextIds actually resolve to the same Context?

See Also

• Higgins Home
• Higgins Wiki
• Concepts