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Many of you will think of a broken record when you hear this, but I never tire
of saying it. {grin}
If your need is essentially to put a literal property on objects (whether that
be a title or the name of a collection to which the object belongs) you'll
likely get better efficiency using a full-text index (e.g. Lucene or Zebra or
the like). RDF stores really show their strength when supporting structural
queries (e.g. "do _these_ relationships exist between _these_ Fedora-objects?").
To your questions:
Presumably by "Does that mean that all Fedora relations must be uris?" you mean
"Does that mean that [the objects of] all Fedora relations must be uris?". The
answer is no. Certainly you can use literals as objects. But the relationships
in the Fedora ontology (from which you drew <isMemberOfCollection>) have
specified semantics that aren't in your control. In the case of
<isMemberOfCollection>, the semantics include the expectation that the object
of this predicate is indeed a Fedora-object, not a literal. So you should be
using your own predicate because <isMemberOfCollection> doesn't have the
meaning you want.
- ---
A. Soroka
Software & Systems Engineering :: Online Library Environment
the University of Virginia Library
On Sep 6, 2012, at 8:27 AM, Scholte, Hans wrote:
> Hi Egbert,
>
> Thanks for the answer.
> Does that mean that all Fedora relations must be uris?
> And if I want a literal then I must make my own predicate?
>
> I solved it now with
>
> <collection xmlns="info:dpc/relations#">ABC_0123</collection>
>
>
> And that works for me (I don't want my collections to be objects in the
> repository (at least, not yet) ).
>
>
> Regards, Hans
>
>
>
>
> -----Original Message-----
> From: Egbert Gramsbergen [mailto:e.f.gramsber...@tudelft.nl]
> Sent: September 06, 2012 12:31
> To: fedora-commons-users@lists.sourceforge.net
> Subject: Re: [fcrepo-user] question sparql/rels-ext
>
> Hello Hans,
>
> First of all: the object of this relation should not be al literal but an uri
> resource.
> So this for collection with PID my:collection:
>
> <isMemberOfCollection
> xmlns="info:fedora/fedora-system:def/relations-external#"
> rdf:resource="info:fedora/my:collection"/>
>
> and your query will be:
> prefix e: <info:fedora/fedora-system:def/relations-external#>
> select ?s
> where { ?s e:isMemberOfCollection <info:fedora/my:collection>}
>
> Second: if the object of a relation is a plain literal you should not use
> rdf:parseType="literal" because that is for xml. Just omit it:
> <someRelation xmlns="some:namespace/">ABC_0123</someRelation>
>
> I hope this helps (and don't forget the info:fedora/ part like I do about 10
> times a day)
>
> Egbert Gramsbergen
> -----Original Message-----
> From: hans [mailto:j.c.m.scho...@uva.nl]
> Sent: donderdag 6 september 2012 10:45
> To: fedora-commons-users@lists.sourceforge.net
> Subject: [fcrepo-user] question sparql/rels-ext
>
> Hi,
>
> I'm trying to add some relations in my rels-ext like so:
>
> <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#";>
> <rdf:Description
> rdf:about="info:fedora/unicum:uba.items.12903be24c35550edd1be17a7b3d9f12">
> <isMemberOfCollection
> xmlns="info:fedora/fedora-system:def/relations-external#"
> rdf:parseType="literal">
> ABC_0123
> </isMemberOfCollection>
> </rdf:Description>
> </rdf:RDF>
>
> When querying the triplestore with
>
> prefix e: <info:fedora/fedora-system:def/relations-external#>
> select ?s
> where { ?s e:isMemberOfCollection 'ABC_0123'}
>
> I have no results
>
> Querying with
>
> prefix e: <info:fedora/fedora-system:def/relations-external#>
> select ?s ?o
> where { ?s e:isMemberOfCollection ?o}
>
> gives me:
>
> "s","o"
> info:fedora/unicum:uba.items.12903be24c35550edd1be17a7b3d9f12,ABC_0123
>
> Why do i not have a result with the first query?
>
> Regards, Hans
>
>
>
> --
> View this message in context:
> http://fedora-commons.1317035.n2.nabble.com/question-sparql-rels-ext-tp7578332.html
> Sent from the Fedora Commons Users mailing list archive at Nabble.com.
>
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