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property path proposals

From: Lee Feigenbaum <lee@thefigtrees.net>
Date: Thu, 27 May 2010 22:33:37 -0400
Message-ID: <4BFF2B81.6030106@thefigtrees.net>
To: SPARQL Working Group <public-rdf-dawg@w3.org>
Thanks to everyone who attended today's dedicated TC on property path 
issues, and a special thanks to Andy for organizing the issues and 
leading the discussion.

Based on the discussions today, we have a bunch of proposals on how to 
resolve open questions regarding the property paths work. If you have 
questions or comments about any of these, please reply in a separate 
thread; if there is not significant dissent, then we'll move to resolve 
these proposals on Tuesday and move on. (As always, future new 
information can change existing resolutions.)

PROPOSED: The ^ inverse path operator is strictly a unary operator.

PROPOSED: Property paths do not preserve the order of underlying graph 
structures (no change to spec).

PROPOSED: Postpone (beyond this WG) any work on returning the length of 
a matched property path.

PROPOSED: The cardinality of solutions to fixed-length paths
is the same as the cardinality of solutions to the path expanded into
triple patterns (with all variables projected); the cardinality of
solutions to variable-length paths is the cardinality of solutions
via paths that do not repeat nodes; the cardinality of solutions to
paths combining fixed and variable length (elt{n,} ) is a combination
of the fixed definition plus the variable definition for paths longer 
than the fixed length.

PROPOSED: Property paths include an operator to negate paths consisting 
of URIs and reverse URIs only.

Two other topics require further work:

+ What nodes match a zero-length path? Greg has an action to send some 
test cases to the list.

+ How do property paths interact with entailment? Discussion is needed 
with the members of the WG most swapped in with the entailment work.

Lee
Received on Friday, 28 May 2010 02:34:18 GMT

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