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Errors from entailment regimes

From: Birte Glimm <birte.glimm@comlab.ox.ac.uk>
Date: Tue, 2 Mar 2010 17:09:55 +0000
Message-ID: <492f2b0b1003020909q2c37fbbbp7085714c7bf0dc56@mail.gmail.com>
To: SPARQL Working Group <public-rdf-dawg@w3.org>, dcharbon@us.ibm.com, lee@thefigtrees.net
Hi all,
since entailment regimes is a time permitting feature, there might not
be teleconf time to discuss this, but there are a couple of occasions
when systems which use non-simple entailment might want to throw
entailment specific errors. I went through the ent regime spec and
looked at what kind of errors HermiT can throw and these things seem
to be needed:
1) An error that indicates that the graph is not well-formed for the
regime. In OWL with Direct Semantics and in particular in the OWL
Direct Semantics profiles not all graphs are legal and this error
would indicate that the system cannot deal with the triples in the
active graph for the query. I guess that would still count as query
fault, e.g., of the form
   <fault name="MalformedGraphForEntailmentRegime"
element="st:malformed-graph-for-entailment-regime"/>
2) Under OWL Direct Semantics also BGPs can be malformed, i.e., the
BGP cannot be mapped into OWL objects. At the moment that results in
an empty query answers and is not an error, but we might want to
change that. In the latter case that would result in an error such as
   <fault name="MalformedBGPForEntailmentRegime"
element="st:malformed-bgp-for-entailment-regime"/>
3) An error that systems can throw when the queried graph is
inconsistent and the system has detected that.
   <fault name="InconsistentGraph" element="st:inconsistent-graph"/>
4) Systems that implement the OWLReasoner interface can be configured
to raise an error if queries contain names that don't occur in the
graph. E.g., if I have a query with BGP: ?x a ex:C and ex:C that mean
the reasoner (again this applies to Direct Semantics) should compute
individuals that have (unknown) type ex:C. HermiT by default allows
such queries and we just switch to raising such errors in rare cases,
e.g., because it is useful to detect namespace errors. I personally
can live with just allowing such queries. They don't really do any
harm IMO.

Maybe somebody else has something to add. Other errors such as syntax
errors in the query etc are already captured in the protocol. Timeouts
seem to be handled as refused requests, so that's covered too.

Birte


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Received on Tuesday, 2 March 2010 17:10:28 GMT

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