Hi Mikael,
Thanks for the comments. I agree with you about Case 3.
So when can we expect a model-theoretic semantics for the DCAM ;)
Cheers,
Al.
Mikael Nilsson wrote:
> Hi Alistair!
>
> Thanks very much for an interesting analysis! It helps a lot with the
> current thinking in the DC RDF draft.
>
> Generally, I think the analysis is sound. I do have a few comments, so
> here we go:
>
> -----
> "Because the DCAM does not have a model theory (i.e. it does not have a
> formal semantics) the mapping here is based on a purely structural
> analysis of the models."
>
> That cannot be really true. The lack of a *formal* model theory does not
> mean that DCAM is completely void of semantics, even though it is
> informal. Thus, I don't feel it's accurate to say that the analysis is
> based purely on the structure. You do make references to this informal
> semantics in several places... (Case 5 comes to mind)
>
> -----
>
> Case 1 should probably be removed from the DCAM. I've added this to the
> issues list:
>
> http://dublincore.org/architecturewiki/AMIssues
>
> -----
>
> Why is Case 3 not a special case of Case 4, with n=1? I'm lacking a
> version 3b, similar to 4b. I actually find the mapping in case 3 to be
> very controversial :-)
>
> -----
>
> We are currently suggesting the introduction of a dcrdf:valueString
> property, which would be a sub-property of rdf:value, playing the role
> of rdf:value in your analysis.
>
> -----
>
> Generally, it's probably fair to say that your case a) in cases 4, 6, 7,
> 8 and 9 correspond to the union of the previous two recommendations
> (dcmes-xml and dcq-rdf-xml), while case b corresponds to what we do in
> the new DC RDF binding draft.
>
> You should maybe note that, and also note that the "b" cases are the
> only ones with reasonably well-defined semantics for the properties
> involved... (as noted in case 6, but this note is more general...)
>
> -----
>
> Re: datatypes, there's a special case in the draft that you might want
> to look at.
>
> Also, the possibility of both a syntax encoding scheme and a language
> has been noted as an issue, and I'd say is a likely candidate for
> removal.
>
> -----
>
> Rich descriptions are supported by a simple rdfs:seeAlso property. That
> will not support anything you might think of, but will cover some
> important cases.
>
> -----
> "Expressing Dublin Core metadata in terms of RDF is commonly viewed as
> just another encoding syntax, however this is a misconception. RDF has
> its own model and semantics, and therefore defines its own set of
> interpretation rules (@@TODO ref). In order to express Dublin Core
> metadata as an RDF graph, we therefore have to understand the mapping
> between the DCMI abstract model and the RDF model theory. Because SKOS
> is itself an application of RDF, its semantics are defined entirely in
> terms of the RDF model theory, and therefore in order to use SKOS and
> DCMI metadata terms in combination we need to be able to map DCMI
> metadata semantics into RDF."
>
> I agree generally with your statement that the DC RDF encoding is not a
> simple "representation" or "encoding" of Dublin Core. It's a matter of
> mapping from one framework to another, richer framework. The situation
> can be described using this diagram:
>
> DC ------------> World
>
> |
> | ^
> | |
> v |
> |
> RDF ----------------
>
> Thus, we're in a situation where DC metadata can be interpreted in the
> world "directly", or it can be mapped to RDF and then interpreted in the
> world using the RDF semantics.
>
> What we've tried to do in the new DC RDF "encoding" is make sure that
> this diagram commutes in mathematical terms.
>
> In other words, make sure that given a DC metadata fragment "m", the
> following operations
>
> dcam_interpretation(m)
>
> rdf_interpretation(dc_rdf_mapping(m))
>
> end up at the same place in the "world".
>
> Or in simpler terms: that interpreting DC metadata using DCAM directly,
> or by mapping to RDF and then using the RDF semantics on that piece of
> RDF, means the same thing.
>
> (As a mathematician, I'm very happy with the above diagram, BTW ...)
>
> Thanks for stimulating my thoughts :-)
>
> /Mikael
>
> tor 2006-05-04 klockan 12:07 +0100 skrev Alistair Miles:
>> Hi all,
>>
>> I've done a short comparison of the DCMI abstract model with the RDF
>> concepts and abstract syntax, as part of a larger paper I'm trying to
>> write on SKOS. It's online at:
>>
>> http://isegserv.itd.rl.ac.uk/public/skos/press/dc2006/rdfdcam.html
>>
>> I don't know if it bears directly on the domains and ranges discussion,
>> and I haven't read Mikael's new draft yet, but I thought I'd post it now
>> in case it's useful. Comments welcome.
>>
>> Cheers,
>>
>> Alistair.
>>
>>
--
Alistair Miles
Research Associate
CCLRC - Rutherford Appleton Laboratory
Building R1 Room 1.60
Fermi Avenue
Chilton
Didcot
Oxfordshire OX11 0QX
United Kingdom
Web: http://purl.org/net/aliman
Email: [log in to unmask]
Tel: +44 (0)1235 445440
|
