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DC-ARCHITECTURE  February 2012

DC-ARCHITECTURE February 2012

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Subject:

Re: DCAM: the analogy to SKOS

From:

Karen Coyle <[log in to unmask]>

Reply-To:

DCMI Architecture Forum <[log in to unmask]>

Date:

Sun, 5 Feb 2012 12:04:58 -0800

Content-Type:

text/plain

Parts/Attachments:

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text/plain (377 lines)

On 2/2/12 8:15 AM, Antoine Isaac wrote:

> As a matter of fact SKOS was firstly designed as a quick/cheap way to
> port KOS data on the Semantic Web. In an ideal world, all the resources
> in thesaurus or gazetteers, etc should be re-worked on and represented
> as "real" persons, places, events, etc, and not as "concept", "terms" or
> any other weird "knowledge artifacts". Many people in the Semantic Web
> community would like that SKOS would be used only for what is for them
> "true concepts" (freedom, justice, data modelling, etc)!

This is, of course, an ontological distinction, using 'ontology' in its 
original philosophical sense of a study of reality. If the SW is going 
to be an open world, it seems that it cannot define reality in only one 
way. That means that it needs to be possible for something like 
"California" to be both a geographic place and a topic, depending on how 
the user has defined it.

I view SKOS as a light-weight markup for the international standard on 
thesaurus construction. If you create something like:

California
   Broader term: USA
   Narrower term: San Francisco

then you are ontologically dealing in concepts, since "BT" and "NT" are 
defined as broader and narrower "concepts" if you are following 
thesaurus construction rules.

As with many SW "applications," SKOS defines some properties that are 
generally useful, such as pref/alt/hidden labels. I think that things 
get confused when these get used outside of the KOS application of SKOS 
because I think it isn't clear to folks whether they are "doing KOS" or 
not at that point. They have to think about exactly what "pref" means as 
defined in SKOS and determine if it can be used for their need outside 
of SKOS.

This is a conversation I have often had with Tom about context - context 
may not matter a lot in data processing, but humans generally function 
within conceptual contexts, whether they are aware of it or not. Many of 
us are unable to become machine-like enough to divorce something like 
"prefLabel" from its context. I have this problem with foaf:Person - is 
it the same as FRBR:Person? Or MARC x00? It's definition says one thing, 
but its context tells me otherwise.

I see DCAM as being a set of patterns that can be made out of basic RDF. 
If RDF is the atom, DCAM is the element set (as in periodical table of 
elements). The advantage I see with DCAM is that it is not within a 
specific application context, and therefore can deal with general 
structures that aren't going to be confused with their role in an 
application.

kc

>
> So SKOS itself can be seen as relevant to the level of DCAM, i.e. the
> "data-structuring" one, and to the one of "world-modelling".
>
> Therefore, the connections at [1] still seem right. And I'd find it
> difficult to prove the DCAM/SKOS analogy wrong. But still, it results in
> a picture that is not easy to grasp, let alone explain to others! So
> maybe the analogy (which I think is based on "SKOS as a KOS data
> structure") is less productive than we thought first.
>
> In fact perhaps the analogy to SKOS is mostly relevant in terms of the
> "introductory sentence to SKOS", quoted by Tom earlier. It seems that we
> could re-use the structure of that argument to fit DCAM's "missions"
> into a nice punchline.
>
> Best,
>
> Antoine
>
> [1] http://wiki.dublincore.org/index.php/DCAM_Revision_Gap_Analysis
>
>
>> Hi all
>>
>> I've been trying to follow the discussion on DCAM revision, and I must
>> confess I've been totally confused so far on what the conversation was
>> all about until this post from Pete, which is the first I fully
>> understand and agree with.
>> To try and understand more other viewpoints, I have a slightly
>> provocative question : what is the use of the current DCAM so far,
>> outside the DCMI standards?
>> If I look from the RDF vocabularies ecosystem, the answer is : nobody
>> AFAIK :(
>> Compare the reuse of DC Terms and DCAM at
>> http://labs.mondeca.com/dataset/lov/details/vocabulary_dc.html
>> http://labs.mondeca.com/dataset/lov/details/vocabulary_dcam.html
>>
>> Of course the current content at
>> http://dublincore.org/2010/10/11/dcam.rdf is minimal, but one would
>> think that the very generic class dcam:VocabularyEncodingScheme would
>> be re-used here and there. One would expect for example things like
>>
>> skos:ConceptScheme rdfs:subClassOf dcam:VocabularyEncodingScheme
>> See discussion
>> http://lists.w3.org/Archives/Public/public-esw-thes/2010Jan/0007.html
>>
>> Is my question coming from a narrow-minded view from RDF land? If yes
>> change my question to :
>> Who *else" outside RDF land and DCMI standards cares or should care
>> about DCAM? And why?
>>
>> Maybe a preliminary answer to this question would help me understand
>> where this debate is bound to.
>>
>> Thanks for your time
>>
>> Bernard
>>
>>
>> 2012/2/1 Pete Johnston <[log in to unmask]
>> <mailto:[log in to unmask]>>
>>
>> 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
>> E: [log in to unmask] <mailto:[log in to unmask]>
>> T: +44 (0)1225 474323 <tel:%2B44%20%280%291225%20474323>
>> F: +44 (0)1225 474301 <tel:%2B44%20%280%291225%20474301>
>> www.eduserv.org.uk <http://www.eduserv.org.uk>
>> Eduserv is a company limited by guarantee (registered in England &
>> Wales, company number: 3763109) and a charity (charity number
>> 1079456), whose registered office is at Royal Mead, Railway Place,
>> Bath, BA1 1SR.
>>
>>
>> > -----Original Message-----
>> > From: DCMI Architecture Forum [mailto:DC- <mailto:DC->
>> > [log in to unmask] <mailto:[log in to unmask]>] On
>> Behalf Of Thomas Baker
>> > Sent: 26 January 2012 23:31
>> > To: [log in to unmask]
>> <mailto:[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] <mailto:[log in to unmask]>>
>>
>>
>>
>>
>> --
>> *Bernard Vatant
>> *
>> Vocabularies & Data Engineering
>> Tel : + 33 (0)9 71 48 84 59
>> Skype : bernard.vatant
>> Linked Open Vocabularies <http://labs.mondeca.com/dataset/lov>
>>
>> --------------------------------------------------------
>> *Mondeca** ** *
>> 3 cité Nollez 75018 Paris, France
>> www.mondeca.com <http://www.mondeca.com/>
>> Follow us on Twitter : @mondecanews <http://twitter.com/#%21/mondecanews>
>>

-- 
Karen Coyle
[log in to unmask] http://kcoyle.net
ph: 1-510-540-7596
m: 1-510-435-8234
skype: kcoylenet

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