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Allowing URIs as identifier values (in a differently named property) seems
> to correspond with the "identifies" property proposed in
> < http://www.w3.org/community/schemabibex/wiki/Identifier >: At a first
> glance I found it silly that a thing has an identifier which in turn
> identifies a (i.e. this?) thing. But if insulate the graph for the
> identifier and read "identifies" as "is commonly used for" then it is
> exactly the property I was reasoning about.
>

The important point here is the relationship between the two different
resources.

If both URIs identify the same "thing", in this case a real world person,
then IMO the correct predicate is owl:sameAs, and there is no need for a
bf:Identifier.

For people, where there isn't any need for interpretation, this is
relatively easy.  Either a URI identifies me, or it doesn't.  For more
resources that require interpretation, such as bf:Work, or Topic, the
same-ness is much trickier to determine as the exact nature of the resource
is difficult (I might even say impossible) to determine.  Thus whether an
ISBN identifies exactly the same "thing" as another similar identifier is
much trickier.



> Now consider
> <http://example.org/persons/kcoyle> a bf:person;
>    bf:identifier [
>        bf:schema "VIAF";
>        bf:identifierValue "195531823";
>        bf:identifierValueURI <http://viaf.org/viaf/195531823>
>      ].
>

Or ... <http://example.org/persons/kcoyle> owl:sameAs <
http://viaf.org/viaf/195531823> .


This states identity of <http://example.org/persons/kcoyle> with
> any resource carrying matching identifieres, e.g.
> <http://example.com/p/kc> a bf:person;
>    bf:identifier [
>        bf:schema "VIAF";
>        bf:identifierValueURI <http://viaf.org/viaf/195531823>
>      ].
>

Or ... <http://example.com/p/kc> owl:sameAs <http://viaf.org/viaf/195531823>
.



> However identity with the resource <http://viaf.org/viaf/195531823>
> is NOT built into that construction, it's rather "all resources
> relating the same way with <http://viaf.org/viaf/195531823>
> are pairwise equivalent" and someone would /explicitly/ have to add
>
> <http://viaf.org/viaf/195531823> a bf:person;
>    bf:identifier [
>        bf:schema "VIAF";
>        bf:identifierValueURI <http://viaf.org/viaf/195531823>;
>        bf:identifierValueURI <http://viaf.org/195531823>;
>        bf:identifierValueURI <http://viaf.org/viaf/sourceID/LC|n89613425>;
>      ].
>

And here is demonstrated the issue with approaches like this...

X a class ;
  bf:identifier Y .
Y a bf:Identifier ;
  bf:identifierValueURI X .

is unnecessary circularity.  Also, having multiple bf:Identifiers, or
multiple values on a single blank node like above introduces additional
tiers of semantic complexity.

Rob