Hi all,

as a strong promoter for the RDF basis for DCAM, I would like to 
emphasize, too, that RDF is only the formal model and should not be seen 
as a concrete syntax. JSON is a syntax, it has no semantics. I like it 
very much, and I like simple, pragmatic implementations, but that's not 
what we need in our current context.

In the W3C provenance WG, we just had the experience, that it is much 
easier to discuss a model that is defined in a formal language, in 
contrast to plain English, which lead to endless discussions before. We 
now focus on the formal PROV ontology, written in OWL, to reach a 
consensus about the model. Additionally, we of course create documents 
in plain English (at least) that hopefully explain and demonstrate what 
can be done with the model. But these drafts can not be used to define 
the model in the first place.

I think the only formal language that we all speak is {RDF,RDFS, OWL}, 
that's why I want to focus on the definition of everything that we are 
talking about in DCAM with this language. In that respect, it is more a 
side-effect that this would end in actually being RDF. If we face 
limitations in this formal language that we can not accept, then of 
course we should not restrict ourselves to RDF. But only then.

Cheers,

Kai


Am 15.02.2012 16:55, schrieb Thomas Baker:
> On Wed, Feb 15, 2012 at 08:49:32AM -0500, Jon Phipps wrote:
>> I've been doing some wandering around in JSON land for the last few days
>> and, as part of a continuing observation that RDF is an implementation
>> detail rather than a core requirement, I'd like to point to this post from
>> James Snell
>> http://chmod777self.blogspot.com/2012/02/mostly-linked-data.html
>> And the JSON Scema spec: http://json-schema.org/
>
> It looks to me like he considers RDF to be a "format" and, as such,
> comparable to JSON.  Commenting on [1], he writes:
>
>      Reading on a little further, the document goes on to expand on that third
>      point, "In order to enable a wide range of different applications to
>      process Web content, it is important to agree on standardized content
>      formats. The agreement on HTML as a dominant document format was an
>      important factor that made the Web scale. The third Linked Data principle
>      therefore advocates use of a single data model for publishing structured
>      data on the Web – the Resource Description Framework (RDF), a simple
>      graph-based data model that has been designed for use in the context of the
>      Web [70]. The RDF data model is explained in more detail later in this
>      chapter."
>
>      I can absolutely agree with the first part -- that standardized content
>      formats are critical. But the "single data model" bit makes me twitch. We
>      don't need a single data model.. what we need are common conventions for
>      pulling out the bits of information we need regardless of the specific
>      format used.
>
> ...i.e., in my reading, he is equating "data model" with a "specific format".
> As I proposed yesterday, I think it is important to distinguish between RDF
> "the model and abstract syntax" and RDF/XML "the concrete serialization syntax,
> or format" -- not to mention other concrete RDF syntaxes such as N-Triples and
> Turtle -- in DCAM's general message:
>
>      The Dublin Core Abstract Model (DCAM) provides a language for representing
>      the structure of specific Metadata Records -- put more abstractly, to
>      specify a Description Set Profile -- in a form that is independent of
>      particular Concrete Encoding Technologies such as XML Schema, RDF/XML,
>      RelaxNG, relational databases, Schematron, or JSON.
>
>      In order to provide compatibility with Semantic Web and Linked Data
>      applications, however, DCAM is fully aligned with the Model and Abstract
>      Syntax of RDF.  (Note that the RDF abstract model is the basis for -- thus
>      distinct from -- concrete RDF encoding technologies such as RDF/XML,
>      N-Triples, and Turtle.) Knowledge of RDF is not a prerequisite for
>      understanding DCAM on an informal level.
>
> It would help if we could agree on a way to characterize this distinction
> (e.g., "Concrete Encoding Technologies" versus "Model and Abstract Syntax").
>
> Unless I'm missing the point of his argument, I do not think James Snell is
> proposing JSON Activity Streams as a generic abstract syntax -- something which
> would compete with RDF as a "grammatical" basis for interoperability in Linked
> Data.  He emphasizes his point that "If you're familiar with Activity Streams
> and the linking extensions, then you'll know exactly what to do with this."
> That seems consistent with what we want to do with DCAM -- with the added
> distinction that if a JSON format is aligned with DCAM, and DCAM is aligned
> with RDF, then one would in principle be able to express the contents of a JSON
> format using an RDF concrete syntax.  Indeed, James's formulation that "what we
> need are common conventions for pulling out the bits of information we need
> regardless of the specific format used" could almost be used verbatim in a
> description of the DCAM we are discussing.
>
> Jon writes:
>> as part of a continuing observation that RDF is an implementation
>> detail rather than a core requirement...
>
> I am coming around to the idea that DCAM (or at any rate, "DCAM 2") might be
> presented informally without emphasizing RDF, and that some people might find
> such a DCAM useful as a very high-level way to conceptualize metadata (i.e.,
> Statements, composed of Slots for information and grouped into Descriptions and
> Description Sets, following common design patterns, etc...) I still do not see
> the value of specifying a DCAM that is anything less than perfectly aligned
> with the RDF Model and Abstract Syntax.  That people may take inspiration from
> such an RDF-grounded model, ignoring the RDF basis, is not something we should
> worry about.  But RDF, such as it is, is the only common _grammatical_ basis
> for data that we currently have, and not to ground DCAM in RDF would make it
> useless for the purposes of RDF-based interoperability.
>
> Tom
>
> [1] http://linkeddatabook.com/editions/1.0/
>
>

-- 
Kai Eckert
Universitätsbibliothek Mannheim
Stellv. Leiter Abteilung Digitale Bibliotheksdienste
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