From: Enrico Franconi <franconi@inf.unibz.it>

Date: Fri, 27 Jan 2006 18:46:23 +0100

Message-Id: <59135ECA-DF9B-4B6C-AEC3-B820203ABF6B@inf.unibz.it>

Cc: pfps@inf.unibz.it

To: RDF Data Access Working Group <public-rdf-dawg@w3.org>

Date: Fri, 27 Jan 2006 18:46:23 +0100

Message-Id: <59135ECA-DF9B-4B6C-AEC3-B820203ABF6B@inf.unibz.it>

Cc: pfps@inf.unibz.it

To: RDF Data Access Working Group <public-rdf-dawg@w3.org>

These change requests are the outcome of discussions with external semweb people. They are purely editorial, the definitions stay the way they are in v1.623, and their purpose is to have a clearer explanation of the definitions. 1) The definition of graph-equivalence between BGPs should be either really formal (option a, adapted from <http://www.w3.org/TR/2004/REC- rdf-concepts-20040210/#section-graph-equality>), or informal in the text (something like option b). The way it is now is semi-formal and incorrect. option a) """ Two basic graph patterns BGP and BGP' are graph-equivalent if there is a bijection M between the sets of nodes of the two basic graph patterns, such that: 1. M maps blank nodes to blank nodes. 2. M(lit)=lit for all RDF literals lit which are nodes of BGP. 3. M(iri)=iri for all RDF IRI references uri which are nodes of BGP. 4. M(var)=var for all query variables var which are nodes of BGP. 5. The triple ( s, p, o ) is in BGP if and only if the triple ( M (s), M(p), M(o) ) is in BGP'. """ option b) """ Two basic graph patterns are graph-equivalent if they are the same up to bnode renaming. """ 2) Definition of scoping set does not emphasise the simple fact that in general it is an arbitrary subset of the RDF terms. So I propose: """ A Scoping Set B is an arbitrary subset of the RDF terms. """ 3) Typo in the definition of scoping graphs (s/The/A/). """ The Scoping Graph G' for RDF graph G, is an RDF Graph that is graph- equivalent to G """ --> """ A Scoping Graph G' for RDF graph G, is an RDF Graph that is graph- equivalent to G. """ 4) The role of E-entailment is too fuzzy. I propose the following at the beginning of the Section. """ A basic graph patterns is a set of triple patterns and forms the core of SPARQL queries. Matching a basic graph pattern is defined in terms of some unspecified entailment regime to allow for future extension of the language. Definition: E-entailment regime An E-entailment regime is a relation between a subset of RTD graphs and a subset of basic graph patterns. A basic graph pattern in the range of an E-entailment is called well- formed for the E-entailment. Examples of E-entailment are simple entailment [RDF-MT], RDF entailment [RDF-MT], RDFS entailment [RDF-MT], OWL entailment [OWL- Semantics]. This specification covers only simple entailment [RDF-MT] as E-entailment. """ The "Definition: Basic Graph Pattern" should be called "Definition: Basic Graph Pattern E-matching". """ Definition: Basic Graph Pattern E-matching Let E-entails be an E-entailment regime, BGP a basic graph pattern, G an RDF graph, G' a scoping graph for G, B a scoping set, and S a pattern solution. BGP E-matches G with pattern solution S with respect to a scoping graph G' and scoping set B, if there is a basic graph pattern BGP' that is graph equivalent to BGP, such that: 1/ G' and BGP' do not share any blank node labels, 2/ (G' union S(BGP')) is a well-formed graph for the E-entailment, 3/ G E-entails (G' union S(BGP')), 4/ The range of S is equal to B. """ Comments? --e.Received on Friday, 27 January 2006 17:46:35 GMT

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