Difference between revisions of "ContextId"

Revision as of 00:22, 1 February 2008

This page describes and defines a Higgins ContextId.

A ContextId is a kind of Attribute that uniquely identifies the instance of a Context that contains it.
The value of a ContextId MUST be a single instance of a ContextIdDatatype.
Two different ContextIds may refer to the same Context.
If the value of a ContextId is resolvable, its value should dereference the information necessary to discover how to access a Context. See Context Discovery.

It is not required for a ContextIds to resolve to a Context instance in which case this is referred to as an abstract ContextId. However, most Contexts are not abstract, and can be resolved a network (or local) data access service to discover the information necessary to access the Context.

The Identity Attribute Service (IdAS) can be used as a service to access a Context given a ContextId.
If two ContextId's values are equal, they refer to the same underlying Context, although not necessarily the same Context "container" instance returned by IdAS. This means that, as a requester of information, different clients of IdAS may see different subsets of the Context based on the authorization passed in during authentication.
A given ContextId may be used against multiple Context Providers to produce the same Context (although, as mentioned, different Context instances).

@@ Line 5: / Line 5: @@
 * A [[ContextId]] is a kind of [[Attribute]] that uniquely identifies the instance of a [[Context]] that contains it.
 * The value of a [[ContextId]] MUST be a single instance of a [[ContextIdDatatype]].
+* Two different [[ContextId]]s may refer to the same [[Context]].
 * If the value of a [[ContextId]] is resolvable, its value should dereference the information necessary to discover how to access a [[Context]]. See [[Context Discovery]].