Mappings (was IVOAT)

[Alasdair Gray]

Hi,

Comments below preceded by an [AG].


-----Original Message-----
From: owner-semantics at eso.org [mailto:owner-semantics at eso.org] On Behalf
Of Frederic V. Hessman
Sent: 30 November 2007 15:09
To: IVOA semantics
Subject: Re: Mappings (was IVOAT)

[snip]

> Rick has declared the mappings using the skos:related property and  
> embedded these within the skos version of the vocabulary.   First  
> of all, I feel that the mappings between vocabularies should be  
> kept completely separate from the skos version of the vocabulary.   
> This allows us to Concentrate on generating clean versions of the  
> vocabularies. Change the mappings without needing to amend the skos  
> version of the vocabulary. Use different mappings in different  
> circumstances if this meets our needs.
>
Good point - hadn't thought of that.   Does this suggests, however,  
that we'll need a full matrix of RDF conversion files?

[AG] Not necessarily a full matrix but certainly it is possible that one
vocabulary may be mapped to many other vocabularies. One of the main
goals of my current project is to investigate using "chains" of
mappings. Thus, if you have a mapping from A to B and another from B to
C, can these be linked together to related terms from A to terms in C.

		A.rdf	B.rdf	C.rdf

A.rdf	N/A		A2B.rdf	A2C.rdf

B.rdf	B2A.rdf	N/A		B2C.rdf

C.rdf	C2A.rdf	C2B.rdf	N/A

Ugh!   Thank goodness I'm only really interested in tokens....
> Second, I feel that the skos:related property is the wrong way to  
> relate concepts in different vocabularies. My interpretation of the  
> skos core, although it is not explicitly stated, is that the  
> properties skos:related, skos:broader, and skos:narrower, are for  
> defining relationships between concepts in a single vocabulary. We  
> should be looking to use the SKOS mapping vocabulary specification  
> [1] for this purpose. This provides several properties for mapping  
> between concepts in different vocabularies. (I am in the process of  
> declaring such mappings between the A&A Keywords and the AOIM  
> vocabularies. Once I have completed this I will send it around the  
> list.)
>
Sorry - my attention span for W3C documentation is obviously  
limited.    And I thought only young people had this problem.....

[AG] What you did is not necessarily wrong, the documentation does not
prevent you from using skos:related/skos:broader/skos:narrower to relate
concepts from different skos:ConceptSchemes. However, I feel that it
would be cleaner to use the skos mapping vocabulary for the purpose of
mapping between vocabularies. This is because it makes explicit that
there is a difference, for example, between a broader relationship
within one vocabulary and a broader relationship between terms in
different vocabularies.

Alasdair

Alasdair J G Gray
Research Associate: Explicator Project
http://explicator.dcs.gla.ac.uk
Computer Science, University of Glasgow
0141 330 6292