# Re: Editorial changes in Section 2.5

From: Pat Hayes <phayes@ihmc.us>
Date: Mon, 30 Jan 2006 13:22:23 -0600
Message-Id: <p06230904c004164dc164@[10.100.0.23]>
To: Enrico Franconi <franconi@inf.unibz.it>, Andy Seaborne <andy.seaborne@hp.com>
Cc: RDF Data Access Working Group <public-rdf-dawg@w3.org>
```
>"""
>Definition: Basic Graph Pattern equivalent
>Two basic graph patterns are basic graph pattern equivalent if there
>is a bijection between the nodes of the triple patterns that maps
>blank nodes to blank nodes and maps variables, literals and IRIs to
>themselves.
>"""
>
>Mmhhh, I'm not sure it is correct :-(
>You need to maintain the structure, not only the nodes (item 5. below)...
>I still believe that either we have the real formal notion, or just
>the informal one:
>
>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'.
>"""

Perhaps we can compromise on the style without sacrificing precision.

Two basic graph patterns are equivalent if there is a bijection M
between the terms of the triple patterns that maps blank nodes to
blank nodes and maps variables, literals and IRIs to themselves, such
that a triple ( s, p, o ) is the first pattern if and only if the
triple ( M(s), M(p) M(o) ) is in the second. This generalizes the
notion of 'equivalence' between RDF graphs.

(We can use the same terminology for equivalence of graphs and of
patterns, since it is essentially the same notion.)

Pat

>option b)
>"""
>Two basic graph patterns are graph-equivalent if they are the same
>up to bnode renaming.
>"""
>
>
>--e.
>
>Attachment converted: betelguese2:smime 17.p7s (    /    ) (00230501)

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Received on Monday, 30 January 2006 19:22:30 UTC

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