Re: Proposing Tracker for inclusion into GNOME 2.18

2006-10-24 klockan 17:26 skrev James Henstridge:
> I think that the idea Ross is trying to get across here is that rather
> than having a flat namespace of metadata types, you want to have
> relationships between the metadata types (metadata about metadata).

Enter RDF, RDFS and OWL.

> For example, we might have a have a relationship that says that "ross
> performed song.ogg" is a specialised version of "ross created
> song.ogg".  Another simple relationship between metadata types might
> be that "ross created song.ogg" implies "song.ogg was created by
> ross".

This is exactly what rdfs:subPropertyOf means.

> The idea is that these implicit relationships would be used in
> queries, so if we have the relationship "ross performed song.ogg" in
> the database, then song.ogg will be picked up by the query "files
> created by ross".  At the same time, the file would not get picked up
> by a query for "files photographed by ross".

This is exactly what owl:inversePropertyOf means.

> This is particularly important in a system with an extensible metadata
> system.  If app developers can introduce arbitrary new metadata types,
> it would be nice to know how they relate to other existing types.

This is exactly what rdfs:subClassOf and rdfs:subPropertyOf are meant for.
Furthermore, the various OWL relations can be used to express relations
between metadata (both classes and properties).

> As another example, consider a developers experimenting with a new
> class of application.  Lets say that two projects define some metadata
> types for the files that they produce respectively.  These types will
> be distinct (hopefully there is something in the spec for namespacing
> custom metadata), but a user might want to search both types of
> documents.

This is what rdf:type and rdfs:subClassOf are designed for.

> So it would be nice if the metadata query system could be told that
> sets of metadata types are equivalent.  If the apps mature and agree
> on a common set of metadata types, they'd probably want to include
> mappings between the new standard types and the legacy ones.

Once again, see the Semantic Web specifications ;)

  mvrgr, Wouter

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it's very scary :: fighting snake                              -- underworld

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