David,
The presence in a resource description (or record or set) of
DC.Relation.FOO = BAR
is an assertion that "something" stands in relation FOO to resource BAR.
What that "something" is may perhaps be specified in at least two ways:
(a) for non-embedded (standalone) metadata, DC.Identifier may specify it,
and (b) for embedded metadata, the surrounding resource is usually it.
For the non-embedded case (a), we may have violated the mandate that all
elements be optional, since clearly one cannot make sense of DC.Relation
without DC.Identifier's also being present. On the other hand, as I write
this it seems like the same difficulty exists for all non-embedded elements,
i.e., what is the "something" that this non-embedded element DC.Whatever
describes? The answer to that question may be that it is explicitly or
implicitly (by the indexing application) specified, in either the embedded
or non-embedded case.
OK, looks like I've talked myself out of there being any urgent issue here.
Thanks.
-John
=====================
Date: Fri, 23 Jan 1998 14:20:57 -0500
From: David Bearman <[log in to unmask]>
Dear John,
I'm not sure I understand your point. we've just implemented this with in
a test dataset for the Art Museum Image Consortium Library and it seems to
me that bi-directional pointing is explicit with the structure we already
have:
Resource #1
has metadata set #1
in which:
Dc.Identifier=Identifier of Resource #1
DC.Relation.Type=HasFormat
DC.Relation.Identifier=Identifier of Resource #2
Resource #2
has metadata set #2
in which:
DC.Identifier=Identifier of Resource #2
DC.Relation.Type=IsFormatOf
DC.Relation.Identifier=Identifier of Resource #1
it might also have another occurence of DC.Relation.type and
DC.Relation.Identifier with other values, which raises the questions of the
syntax of these things in RDF and how we keep repeating groups in sync, but
that's a different issue (I think) or is it what you are getting at?
are we missing something? Do you want to see the full examples?
David
At 07:10 AM 1/23/98 -0800, John A. Kunze wrote:
>> Date: Fri, 19 Dec 1997 11:53:12 -0500
>> From: David Bearman <[log in to unmask]>
>> ...
>> I. It is important to indicate the relation between one information
>> resource and another in metadata for discovery. Because each information
>> resource may have its own metadata set, these relations need to be
explicit.
>
>David,
>
>I think your report on the Relation semantics is very clear. One missing
>piece is that the resources on either side need to be explicit. Currently
>we only make the second resource explicit (by using its identifier), while
>the first or "present" resource (the resource being described) is implicit.
>This seems to me missing in our discussion and in the basic DC RFC (#1).
>
>There's no problem in situations where the implicit first resource is
>obvious, as in the embedded metadata case. But it's definitely a problem
>in the non-embedded case because we haven't left a place in either Relation
>or Source for the first resource to be indicated.
>
>One solution would be to let Relation (and Source) contain an optional
>extra identifier for the first resource. This would probably help
>implementation of even the embedded case, since that metadata will
>likely be separated from the mother resource when it goes into the
>search system indexes, and there both the first and second resources
>must be explicit.
>
>-John
>
>
>
David Bearman, President
Archives & Museum Informatics
5501 Walnut St., Suite 203
Pittsburgh, PA 15232 USA
ph. + 1-412-683-9775
fax + 1-412-683-7366
email: [log in to unmask]
URL: www.archimuse.com
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