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Editorial changes in Section 2.5

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>

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  

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  

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.

Received on Friday, 27 January 2006 17:46:35 UTC

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