Context Discovery

Design Goals

In addition to all the previous design goals, here are some more that were behind this proposal

• Higgins-ism free. Higgins is not in the service/protocol definition business. So the intuition here is that there shouldn’t be any higgins-isms in the XRDS documents. And there should be nothing special about how ContextIds are resolved to XRDS Service blocks
• Simple things are simple. We want an approach where a OpenID XRI (or URI) can be referred to by a Higgins i-card using a ContextId of the same value as this XRI (or XRI) and presented as an IContext without any modification of the XRDS to which the OpenID XRI resolves. In other words, armed only with an OpenID XRI/URI, the Higgins Identity Agent should be able to present its attributes to the user (read-only) in the i-card manager. OpenID servers don’t need any contextConfig or factoryConfig to use them.
• Complex things are possible. Beyond the simple OpenID case, we also want to support LDAP, SQL, etc. backed Context which do need contextConfig and probably factoryConfig metadata in order to be presented as an IContext.

XRIs/URIs resolving to XRDS documents need to be qualified to be used as ContextIds

• A key issue that is finally resolved in this proposal is that in Higgins a ContextId uniquely identifies a Context whereas an XRI (or URI) that resolves to a single XRDS document can, when looked at as "a provider of attribute sets", provide more than one set of attributes and thus does not uniquely identify a Context in the Higgins sense of the word. For example the XRI =drummond may delegate to an OpenID service and simultaneously to a contact service. The set of attributes (and their values!) provided by each of these two services may be different (and usually are). Thus simply having an XRI does not by itself provide enough information to uniquely specify which possible attribute set we're talking about. [It is also true that this same XRI may have other services unassociated with providing attributes at all (e.g. messaging services), thus underscoring the need to further qualify the XRI from a Higgins perspective]

Use Cases

Use Case	Kind of i-card	ContextId	Context Description	Resolves to	...within which we find the <Service> block by
1	Higgins OpenID URI i-card	=drummond	Drummond's i-name. His i-name provider has provisioned OpenID services for this i-name. This i-name partially identifies a Context holding the attributes provided by OpenID auth	xrds1	matching <Type> element's value of "http://openid.net/server/2.0"
2	Higgins URI i-card	=drummond/vcard/+ldap	Drummond has a (single-DS) Context that holds vcard attributes.	xrds2	matching <Path> element's value of "+ldap"
3	Higgins URI i-card	=drummond/webSurfer/+sql	Drummond uses HBX in his browser and in the Higgins i-card manager he has defined a single-DS Context with the set of attributes he's happy to share with run of the mill websites. It contains only non-identifying information.	xrds3	matching <Path> element's value of "+sql"
4	Higgins URI i-card	@cordance.com/AccountingDept/+ldap	Cordance (Drummond's employer) maintains a directory of all employees. A multi-DS Context.	xrds4	matching <Path> element's value of "+sql"
5	Higgins CardSpace managed i-card	localhost/icardstore/236-86/+ldap	This is the Context behind some card that the Higgins Token Service issued.	xrds5	matching <Path> element's value of "+ldap"

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Use case #1 details

User has an existing OpenID, "=drummond". They wish to manage their OP using the Higgins Identity Agent, specifcally the Higgins i-card manager. They create an OpenID URI i-card using the i-card manager. Note that this is a new specialization of the generic Higgins URI i-card. During the process of creating the new i-card the user types in their OpenID, "=drummond". This is the ContextId of the OpenID URI i-card. The user wishes to see the values of their attributes (i.e. the attributes defined by OpenID authentication) in the i-card manager. Sequence:

1. The OpenID URI i-card invokes an XRI resolver in an IdAS.utils package: XRI.resolveByType("=drummond", "http://openid.net/server/2.0"). The first arg is the ContextId, the second is new; it is the target service <type>. We're telling the resolver to find the <Service> block that matches by matching on <Type> with the value provided. (See XRDS Files section below to see a description of the contents of xrds1)
2. IdAS.open searches IdASRegistry for an IContextFactoryClassName for the http://openid.net/server/2.0 service type, it finds org.eclipse.higgins.cp.openid.
3. That factory initiates itself with the factory config elements (column 3 in IdASRegistry table)
4. We do a <factory>.getInstance reading the “Other <Service> elements” from column 4 in XRDS Files table for the contextConfig data

Use case #2 details

User wants to view the IContext associated with a Higgins URI i-card whose ContextId is "=drummond/vcard/+ldap". Sequence:

1. The i-card manager invokes IURICard.getContext() on this i-card
2. The i-card invokes an XRI resolver: XRI.resolveByPath("=drummond/vcard/+ldap")
3. This resolves to the file "xrds2" and within it the service block whose <Path> element matches "+ldap"
4. We read <Type> value of the same service block and use it in IdASRegistry to look up an IContextFactory class name
5. Use this factory to getInstance an IContext

Use case #5 details

This is an example of a ContextId that will be stored in the metadata of the endpoint reference of the token service in the RST. It will be received by the Token Service, passed to a Token Provider and used by that provider to open up an IContext using IdAS. Mike has verified that MSFT CardSpace preserves this EPR metadata so this same approach will work using Higgins or CardSpace Identity Agents.

XRDS Files (examples)

Each file provides the metadata for the ContextId to which it resolves so that a Higgins Context Provider might be found and that could be told enough about the endpoint to present it as an IContext instance.

The following table shows the elements within the matched <Service> block:

XRDS File	<Type> element's value	<Path> element's value	<Schema> element's value	Other elements
xrds1	http://openid.net/server/2.0	(not present)	(not present)	<URI>url-of-OP</URI>
xrds2	xri-for-ldap	"+ldap"	url-of-schema-for-this-vcard	<SSL>True/False</SSL>,<port/>, and other LDAP-specific elements that identify the context dataset
xrds3	xri-for-sql	"+sql"	(not present)
xrds4	xri-for-ldap	"+ldap"	url-of-schema-for-this-departments-employee-directory	<SSL>True/False</SSL>,<port/>, and other LDAP-specific elements that identify the context dataset
xrds5	xrd-for-ldap	"+ldap"		<SSL>True/False</SSL>,<port/>, and other LDAP-specific elements that identify the context dataset

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Here is what the service block looks like in xrds2:

<Service>
   <Type>xri-for-ldap-type</Type>  
   <Path select="true">+ldap</Path>
   <URI append="none">ldap-server-URL</URI> 
   ...other ContextConfig elements...
</Service>

See http://iss.xdi.org/moin.cgi/IserviceEndpointDefinitions for more examples of I-Service Endpoint definitions.

IdASRegistry

Maps an XRDS service type to an IContextFactory along with any factoryConfig metadata needed (if any)

Service Type	IContextFactory Class Name	other IContextFactory config data
http://openid.net/server/2.0	org.eclipse.higgins.cp.openid	??
xri-for-ldap	org.eclipse.higgins.cp.jndi	??
xri-for-sql	org.eclipse.higgins.cp.slq	??

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Note: "xri-for-ldap" and "xri-for-sql" as used above will be defined by the OASIS XRI TC (they will probably look like say "+i-service*(+ldap)*($v*1.0)" and "+i-service*(+sql)*($v*1.0)"