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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.

Received on Friday, 28 May 2010 02:34:18 UTC

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