ContextId

Introduction

This page describes and defines a Higgins ContextId.

Definition

• A ContextId is a kind of Context Correlation
• A ContextId identifies a instance of a Context
• A ContextId MUST have a single value of type ContextIdDatatype
• If a Context has a ContextId Attribute its value identifies the Context itself.

Details

• The value of a ContextId must directly or indirectly (e.g. by resolution) provide sufficient information to identify a Context. See the Context Discovery with a ContextId heading below.
• Two different ContextIds may refer to the same Context.

ContextId and IdAS

• 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 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 Providers to produce the same Context (although, as mentioned, different Context instances).

Details

• The Identity Attribute Service (IdAS) can be used as a service to access a Context given a ContextId

Some ContextIds are not resolvable to a Context instance. Most Contexts are not abstract. Using a network (or local) data access service their ContextIds are resolvable to data objects that are instantiated and managed by Context Provider plug-ins.

Relationship to OpenID

Any OpenID 2.0 identifier as defined by OpenID Authentication 2.0 may function as a Higgins ContextId. OpenID 2.0 supports both URLs and XRIs. All of the examples of contexthttpURI and contextXRI above are valid OpenID 2.0 identifiers.

The only caveat to keep in mind is that if an OpenID 2.0 URL is used as a Higgins ContextId, the XRDS or XDI document to which it resolves must EITHER contain:

• Only one XRDS service endpoint or XDI context reference describing the target Context, OR
• The consuming application must know how to select the XRDS service endpoint or XDI context reference it requires (i.e., it must know which Higgins Context Type it is seeking).

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.

See Also

• EntityId
• LocalId
• Context Discovery
• Context Discovery Components
• Higgins XRDS Service Endpoint
• Higgins XDI Context Reference
• Concepts

Links

• Higgins Home