Following are the minutes of the unofficial telecon of the XDI TC at:
Date: Friday, 04 January 2013 USA
Time: 9:00AM - 10:30AM Pacific Time (16:00-17:30 UTC)
THE ETHERPAD LINK FOR TODAY IS:
***** DECISION POINTS FOR THIS CALL *****
This week's decision queue is the following set of proposals:
--- EQUIVALENCE LINKS AND REFERENCE LINKS (DRUMMOND & MARKUS)
This proposal has been updated to reflect the consensus to use two different XDI verbs - $ref and $is - to express two different kinds of equivalence.
Drummond noted the following clarification that was added around $is links:
- A $is statement does not trigger any special XDI processing rules. This means that when an XDI endpoint returns a $is statement, it is the client's responsibility to determine if it needs to request the subgraph that is the object of that $is statement.
This is important because a $is statement asserts a non-canonical equivalence between two nodes in the same local graph, which means that both the subject and object of the $is statement may have subgraphs. In this case, a client receiving a response graph that includes a $is statement must decide if it needs to request the subgraph rooted on the object of the $is statement.
Because of this rule, Drummond also added another subrule:
- For this reason, a local root node MUST NOT have a is statement. This avoids the logical entanglement of a graph "containing a copy of itself".
This rule means the "I am" or "who is" statements about the local root node of a graph MUST be expressed with $ref and $is$ref statements and not $is statements. $is statements may only be used for subgraphs.
Drummond also discussed this paper referenced by Giovanni Bartolomeo:
Drummond's assessment was that the distinctions about identity equivalence and the use of owl:sameAs in RDF raised by the paper were very similar to those raised by the separation of $is and $ref in the Equivalence Links proposal. However the key difference is that, since RDF graphs are not addressable, owl:sameAs does not need deal with the notion of canonicality (where only one of the two nodes asserted as equivalent may have a subgraph). So while the specified semantics of owl:sameAs and XDI $is appear to be the same, there is no direct RDF equivalent for $ref.
From the perspective of the attendees on this call, this proposal is now ready to go into Last Call. However we will wait one more call before moving it to that status.
--- DECLARATIVE POLICY _expression_ (DRUMMOND & MARKUS)
This proposal received extensive discussion for the balance of the call since Drummond and Markus were the authors. It was agreed that in addition to $is and $equals for equivalence comparison between XDI nodes and literal values, respectively, and $lesser and $greater for literal value comparison, we also need $matches for literal value string comparison where the match does not have to be an exact match. Markus added this to the proposal on the call.
All TC members are urged to review this proposal soon since declarative policy _expression_ in now in high demand among XDI implementers.
***** DECISION POINT QUEUE REVIEW *****
The decision queue stack is now shown on the following three auto-generated Category pages:
See also this list of proposals that need to be developed:
***** NEXT CALL *****
The next call is next week at the regular time.