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FWIW,

Pete++

Jon


On Wed, Feb 1, 2012 at 12:38 PM, Pete Johnston <[log in to unmask]
> wrote:

> Hi all,
>
> I'm a bit (OK, very!) confused about this analogy between DCAM and SKOS.
>
> To me, SKOS has two components:
>
> - a model of (a part of) the "world" as made up of concepts, concept
> schemes, lexical terms etc, which have certain attributes and certain
> relationships between them
> - an RDF vocabulary (or two if you distinguish base SKOS and SKOS-XL) for
> use in creating RDF graphs/triples to describe that "world"
>
> SKOS is quite generalised so it can condition how we choose to model our
> "worlds" in other domains (e.g. do I model my "places" as SKOS Concepts
> with broader/narrower relations or as spatial things with
> contains/is-contained-by relations? And so on)
>
> But using SKOS doesn't determine/change the nature of my data structures,
> or the "lens" I apply to those data structures; it only changes my "world"
> structures: using SKOS I'm still squarely within the framework of RDF graph
> and triple data structures. SKOS Concept Schemes and Concepts are just more
> "things" in the "world", but in terms of how my data about those things is
> "packaged", SKOS Concept Schemes and Concepts are treated exactly the same
> as any other thing (a foaf:Person, a bibo:Document, a dcmitype:Collection
> etc etc etc).
>
> But - with its notions of Description Set, Description and Statement -
> DCAM does introduce new data structures, or at least (as I prefer to try to
> think of it) a new "lens on", a new way of looking at and referring to
> parts of, the RDF graph/triple structure.
>
> In contrast to SKOS, with DCAM, it's not a question of looking at "the
> world" in a different way. Whether I think of my data as an RDF graph or a
> DCAM Description Set (or as both, depending on how I'm looking at it!), my
> "world" is still the same: it has foaf:Persons who author bibo:Documents
> that are about skos:Concepts that are in skos:ConceptSchemes.
>
> Rather with DCAM, I'm looking at the structure of my _data_ in a different
> way.
>
> So I'm afraid I'm struggling to grasp the significance of comparing the
> DCAM to SKOS - at least at the level that comparison seems to be being
> applied in these discussions. I understood Andy's mention of SKOS on 05/01
>
>
> https://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=DC-ARCHITECTURE;dc1738b9.1201
>
> to be about the practical usefulness of SKOS, the fact that it addresses a
> requirement that people have ("how do I represent my thesaurus using
> RDF?"), not saying that DCAM was something "similar in nature" to SKOS.
>
> Further on in that thread, Kai said on 09/01:
>
>
> https://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=DC-ARCHITECTURE;1fc1d387.1201
>
> > RDF is not only defined for the representation
> > of metadata, it is so abstract that at the same time, it allows for
> instance the
> > definition of ConceptSchemes in SKOS. And if there is a need for the
> > definition of a ConceptScheme, I argue that there is a need for the
> definition
> > of a DescriptionSet, too.
>
> I think this is where I got lost :)
>
> (To me), a SKOS Concept Scheme is just another thing in my "world"
> (alongside a FOAF person etc), another thing to be named with a URI and
> described in my data, my graph, using RDF triples.
>
> But a DCAM Description Set is "a thing in my data", not in my "world".
> Sure, I could name and describe it (just as I could name and describe an
> RDF graph or an RDF triple) but my main "use" of the Description Set notion
> is as a way of structuring my data.
>
> So, from my perspective, I can't help feeling that an SKOS Concept Scheme
> and a DCAM Description Set are very different things, and I'm struggling to
> grasp why comparing them is useful.
>
> I'm not saying it isn't useful, just that, right now, I don't "get it" :)
>
> Pete
>
> Pete Johnston
> Technical Researcher
> Eduserv
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>
>
> > -----Original Message-----
> > From: DCMI Architecture Forum [mailto:DC-
> > [log in to unmask]] On Behalf Of Thomas Baker
> > Sent: 26 January 2012 23:31
> > To: [log in to unmask]
> > Subject: DCAM: the analogy to SKOS
> >
> > In yesterday's Provenance Task Group telecon we found ourselves talking
> > about DCAM [1].  One point of discussion was the analogy of DCAM to SKOS.
> >
> > On January 5, Andy had written:
> >
> > > So I think the pertinent question that needs to be answered pretty
> > > early on in the outer layers of Stuart's onion is "why should I invest
> > > time understanding the DCAM when I could be learning RDF/Linked
> > Data/whatever instead?".
> > >
> > > If we compare the DCAM with, say, SKOS and ask the same kind of
> > > question the answer is more obvious I think - people need to
> > > understand both RDF and SKOS because SKOS gives them something useful
> > > in the area of 'vocabulary' handling that RDF on its own doesn't give
> them.
> > >
> > > The answer for the DCAM is much less clear except in terms of the
> > > original rationale for having the DCAM at all, i.e.
> > >
> > > "It provides an information model which is independent of any
> > > particular [DCMI] encoding syntax. Such an information model allows us
> > > to gain a better understanding of the kinds of [DCMI] descriptions
> > > that we are encoding and facilitates the development of better mappings
> > and cross-syntax translations"
> > > ("[DCMI]" additions by me).
> > >
> > > which, unfortunately, is a very inward looking (and rather narrow)
> > > rationale that is unlikely (as history has shown us) to be of much
> > widespread interest.
> >
> > To which Kai had responded:
> >
> > > [The] analogy to SKOS is perfect, because that was exactly how I
> > > started the RDF-based DCAM wiki page yesterday [1].
> > > Provide DCAM as a model for metadata just like SKOS is for vocabulary
> > > handling.
> > >
> > > [1] http://wiki.dublincore.org/index.php/DCAM_Revision_Tech
> >
> > In yesterday's call, Kai elaborated on the notion of DCAM as an
> equivalent of
> > SKOS for metadata.  I understood him to say that SKOS is an RDF
> vocabulary,
> > but one might also see it as an Abstract Model that could be used by
> people
> > who do not care about RDF.
> >
> > This reminded me that in the Semantic Web Deployment WG, we did in
> > effect try to express a high-level "abstract model" for SKOS (a
> formulation I
> > actually helped write) [2]:
> >
> >     Using SKOS, _concepts_ can be identified using URIs, _labeled_ with
> lexical
> >     strings in one or more natural languages, assigned _notations_
> (lexical
> >     codes), _documented_ with various types of note, _linked to other
> > concepts_
> >     and organized into informal hierarchies and association networks,
> >     aggregated into _concept schemes_, grouped into labeled and/or
> ordered
> >     _collections_, and _mapped_ to concepts in other schemes.
> >
> > ...summarizing the essence of SKOS in just one sentence.  Arguably, this
> is
> > the sort of formulation -- one which does not itself even mention RDF but
> > which maps to RDF in the specification -- we could aspire to make for
> DCAM.
> >
> > I cannot readily formulate one sentence that summarizes what I think DCAM
> > can offer, though it would perhaps be interesting to try.  The story I
> have in
> > mind for DCAM might say that metadata uses items of information --
> strings
> > and URIs, perhaps belonging to sets of strings or URIs (i.e., syntax or
> > vocabulary encoding schemes) -- to describe (make statements about)
> things
> > of interest; that it groups these items into Descriptions about one
> particular
> > thing of interest and groups related Descriptions into Description Sets,
> which
> > are often instantiated in implementations as "records".
> >
> > How these items are used to make meaningful "statements" about things
> > would be the part that one inherits from RDF.  DCAM, as I see it, can
> provide
> > an "interface" to underlying (meaningful) statements by specifying
> patterns
> > of information items grouped into Descriptions and Description Sets.
> >
> > If that is what DCAM is, or should be, then I wonder whether we can
> specify
> > those patterns in enough detail to be useful as an interface to triples
> without
> > becoming too complicated.  In 2007-2008, for example, it seemed
> reasonable
> > to translate "DCAM statements" about value resources using RDF statements
> > with rdf:value and literals or RDF statements with dcam:memberOf and
> > vocabulary encoding scheme URIs [3].  From the perspective of best
> practice,
> > that looks like an oversimplification.  Today, one might want to
> consider using
> > various other properties in statements about a value resource --
> rdfs:label,
> > skos:prefLabel, skos:notation, foaf:name, or dcterms:title... -- though
> > perhaps _not_ rdf:value [4].  Can a DCAM still be defined as an
> interface to
> > triples as straightforward as [4], or would it need to evolve in the
> direction of
> > a more complex and differentiated set of patterns?
> >
> > For discussion on Monday's call (at 11:00 EST)...
> >
> > Tom
> >
> > [1] http://wiki.bib.uni-mannheim.de/dc-
> > provenance/doku.php?id=minutes_2012_01_15
> > [2] http://www.w3.org/TR/skos-reference/
> > [3] http://dublincore.org/documents/dc-rdf/#sect-4
> > [4] http://www.w3.org/2011/rdf-wg/track/issues/27
> >
> > --
> > Tom Baker <[log in to unmask]>
>