[Requirement][SKOS-Core] Local (non-URI) identifiers for concepts

This requirement is split into two parts:


Requirement A

The property skos:externalID was intended to be used to specify any lexical
identifier for a concept that is not a URI. 

Essentially, whereas a URI is a globally unique identifier for a concept,
the value of the skos:externalID property is supposed to be a locally unique
identifier for a concept (i.e. uniquely identifies a concept within the
scope of a specific concept-scheme only). 

I feel the name of the property skos:externalID does not reflect well its
intended meaning and usage, and should be replaced with something that does
so better. 


Requirement B

If we allow concepts to be a member of more than one concept-scheme, then it
becomes ambiguous which scheme the value of a skos:externalID property
should be scoped to. 

So we need some way of saying 'concept X has local identifier Y within the
scope of concept-scheme Z'. 

See also the wiki page <http://esw.w3.org/topic/SkosDev/SkosCore/LocalId>

Al.

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Alistair Miles
Research Associate
CCLRC - Rutherford Appleton Laboratory
Building R1 Room 1.60
Fermi Avenue
Chilton
Didcot
Oxfordshire OX11 0QX
United Kingdom
Email:        a.j.miles@rl.ac.uk
Tel: +44 (0)1235 445440