1. About

This is the home page summarizing progress of the dialog between the XRI TC and the W3C TAG (Technical Architecture Group) regarding the TAG's concerns about XRI 2.0.

3. Progress of the Discussions

4. Primary Open Issue Areas and Proposed Next Steps in Each

On the 2008-08-20 coordination telecon between the XRI TC and W3C TAG, the XRI TC took the action item to:

  1. Write up summaries of the remaining open issue areas.
  2. Identify interrelationships and dependencies between them.
  3. Propose next steps with respect to each issue.

The balance of this wiki page is this writeup. The XRI TC will endeavor to keep this list of issues/next steps current until the discussions are concluded.

5. #1: Abstract Identifier Architecture Issues

The first "bucket" of issues are related to abstract identifier architecture, of which the XRI specifications are an implementation. These issues are all related to each other, and all of them shape the requirements for the other two buckets of issues, so we list these first.

5.1. Abstract vs. Concrete Identifiers

The first issue is the need for a clear definition/model for: a) abstract identifiers for resources, and b) resource descriptors for resources, together a clear explanation of how these co-exist with concrete identifiers for resources and the target resources themselves.

Assigned To

Action Item

XRI TC

Draft document providing definition/model

W3C TAG

Review and comment on this document when it is ready

5.2. Persistence and URN Requirements

One of the requirements for abstract identifiers (but not the only one) is the need for persistent identifiers that can serve as immutable keys when referencing distributed resources. This requirement is generally summarized in RFC 1737 – Functional Requirements for Uniform Resource Names, though there has been additional thinking about the requirements around persistence in the decade since that was published. The open issue is clearly mapping these requirements into the abstract identifier architecture defined above.

Assigned To

Action Item

XRI TC

Address this issue as part of the document above

W3C TAG

Review and comment on this document when it is ready

5.3. Determination By Inspection

One of the XRI TC's other requirements for abstract identifiers is that certain characteristics of the identifier, such as abstractness, persistence/reassignability, and authority, be determinable via inspection (i.e., not require resolution). The open issue is determining whether there is consensus between the XRI TC and the TAG on this requirement.

Assigned To

Action Item

XRI TC

Address this issue as part of the document above

W3C TAG

Review once documented and determine if there is consensus on this requirement

5.4. Other Requirements for Abstract Identifiers

There are other often more compelling requirements for abstract identifiers beyond persistence and inspection, for example structured identifiers and cross-references. The open issue is communicating these requirements clearly enough for the W3C TAG and other interested parties to understand them.

Assigned To

Action Item

XRI TC

Address this issue as part of the document above

W3C TAG

Review and comment on this document when it is ready

6. #2: URI Scheme Issues

The second bucket of issues are related to URI schemes. These issues have cross-dependencies with each other, and also to some extent depend on the conclusions regarding requirements above.

6.1. HTTP URI Profiles

The TAG's position (as summarized in Section 5.5 of their URNs, Namespaces, and Registries finding) is that the XRI requirements should be met by creating a "subclass" of HTTP URI rather than a separate scheme. It is proposed to call such an HTTP URI subclass an HTTP URI profile. The open issues regarding HTTP URI profiles are:

Assigned To

Action Item

W3C TAG

Review these questions and propose initial answers

XRI TC

Review TAG answers and provide feedback

JOINT

If possible agree on a conclusion and next steps

6.2. Rationale for New URI Schemes

Even if some new types of identifiers can be implemented using an HTTP URI profile, the question remains: when does a new type of identifier justify a new URI scheme? This question is important for the XRI TC since it currently has implemented specifications that use the xri: scheme, yet due to procedural misunderstandings, has not yet applied to register this scheme with IANA. So the open issues are:

  1. What are the criteria that justify registration of a new URI scheme?
  2. Does XRI meet these criteria?

Assigned To

Action Item

W3C TAG

Decide how best to proceed to answer question (1)

XRI TC

Review TAG answers to question (1) and provide analysis answering question (2)

JOINT

If possible agree on a conclusion

7. #3: Resolution/Description Issues

The last major bucket of issues regards resolution and resource descriptor architecture. These have some dependencies on the first bucket since resolution/description requirements flow from the requirements of mapping abstract identifiers to target resources. However are largely independent of the second bucket.

7.1. Resource Descriptor Documents as Resources

The first open issue is how resource descriptor documents (also called "discovery documents") are themselves treated as resources from an AWWW standpoint.

Assigned To

Action Item

XRI TC

Address this issue as part of the Abstract Identifier Architecture document in #1 above

W3C TAG

Review and comment on this document when it is ready

7.2. XRDS Discovery Protocol Methods

The second open issue is reviewing the protocol methods currently used (or proposed for the next revision) to discover an XRDS document from either an XRI or an HTTP(S) URI to see if there conform to AWWW recommendations and best practices, and whether the TAG recommends any improvements.

Assigned To

Action Item

XRI TC

Draft a document summarizing the methods currently used/proposed

W3C TAG

Review and comment on this document when it is ready

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