[Tdwg-tag] RDF instead of xml schema
ram at cs.umb.edu
Sat Mar 25 20:33:55 CET 2006
There are very interesting observations about this relationship on the
final pages (pp. 313-314 sic!) of the current revision of the
submission by IBM and others to OMG of an Ontology Definition Metamodel
Metamodels are mechanisms from Model Directed Architecture which, among
other things, are designed to promote interoperability of models, not
merely interoperability of the systems which implement them (which then
comes for free in rigorous MDA, because implementations are a special
kind of model). Users of modeling tools which convert from one model to
another, e.g. code generation from UML, are often the beneficiaries of
formal or informal metamodels in the conversion framework.
[Here I must confess to having read only the TOC and these two pages of
the ODM submission. But from those, I am prepared to speculate that the
rest of it has a lot to say about the topics at hand. Indeed, if it is a
successful metamodel proposal, it will have identified every single
issue raised here in the last few weeks, and more....].
Roderic Page wrote:
> Dear Gregor,
> Various comments:
> Relationship to ER
> In many ways RDF is very like ER-modelling (e.g.,
> http://bit.csc.lsu.edu/~chen/pdf/Chen_Pioneers.pdf), indeed the W3C
> states that "RDF is a member of the Entity-Relationship modelling
> family." One could think of the modelling the link between two entities
> as a triple.
> There's also a comment on this on Danny Ayers' blog
> (http://dannyayers.com/2005/03/16/xml-andor-rdf/) - embedded in some
> other extraneous stuff.
> You might also want to look at D2R Map
> (http://www.wiwiss.fu-berlin.de/suhl/bizer/d2rmap/D2Rmap.htm) for
> mapping between database schema and RDF.
> One way I like to think of this is that I think RDMS are geared towards
> locally held data, hence the emphasis on primary keys and
> normalisation. If, however, much of the data is elsewhere (as I believe
> it is in biodiversity informatics) then you need ways to refer to
> remotely held objects (i.e., URIs, which is another way of saying
> GUIDs). Hence, instead of locally defined primary keys you start to
> store GUIDs (which, by definition, are unique). If you then start to
> think about relationships between the objects identified by GUIDs, then
> you've pretty much got RDF. I would also say that in terms of managing
> local data, RDBMS are not going away. RDF, in my opinion, only really
> becomes relevant once you want to make the data available to others,
> and once you want to enable people to be able to aggregate that data.
Robert A. Morris
Professor of Computer Science
phone (+1)617 287 6466
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