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Thursday, October 28, 2004

Seminar: XML, RDF, Topic Maps, Relational Databases

Update - a comment from Manuel Simoni: Shawn Bower's thesis (PDF).

"XML, RDF, Topic Maps, Relational Databases: So many data models, so little time"

Lois Delcambre, PSU Computer Science / OGI
Monday, November 1, 2004, 12:00pm, FAB 10

One advantage of having different representation schemes and data models is that users can select the right representation and associated tools for their particular need. XML might be a great model to represent some of your information, but maybe sometimes you'd prefer to use RDF for some of your other data. The problem is that multiple representation schemes introduce structural, model-based heterogeneity, making it difficult to combine information from different sources and exploit information using generic tools (e.g., for querying or browsing).

In this work, we are interested in supporting multiple data models and representation schemes in a single, generic representation scheme. We have defined a meta-data-model based representation called the Uni-Level Description (ULD) with a novel architecture to overcome the limitations of typical meta-model based approaches. Unique features of the ULD include:

  • The ULD can accurately describe representation schemes, such as XML and RDF where schema is optional, in addition to traditional database models where a schema must be defined before any data can be entered.
  • The ULD permits data models that support multiple levels of schema or instance-of relationships.
  • The ULD represents the constructs of the data model, schema if present, and data in a single, uniform representation that can be easily used by generic tools.
We have used the ULD to write powerful, generic transformation rules that can even transform data directly from one representation scheme to another. We have also investigated the use of a simple generic browsing capability over information represented in diverse data models and representation schemes.

In this talk, we will motivate and define the ULD and discuss the transformation and browsing applications.

Lois Delcambre is a Professor of Computer Science at Portland State University. She also has a joint appointment as a Professor of Computer Science and Engineering with the OGI School of Science and Engineering at the Oregon Health & Science University. She works in the database field of computer science with a particular interest in database data models as well as other models for structured information including thesaurus models, knowledge representation models, semi-structured models such as XML and RDF, and ontology models.


Anonymous said...

See http://www.cse.ogi.edu/~shawn/bowers-thesis.pdf

Manuel Simoni

Anonymous said...

The dissertation presents that the relational database model, XML, and RDF (which _is_ XML) can be expressed in Prolog(Datalog). The authors then develop a representation (ULD) in Prolog(Datalog) and in other languages.

But we've known that for years, so what's new here?

Patrick Logan said...

First, RDF is not XML, but can be notated in XML.

What's new? Just an interesting description of someone's view of the problem.

Anonymous said...

You're picking nits here, but I can pick nits with the best of them:

Straight from the W3C's RDF Primer at http://www.w3.org/TR/rdf-primer/#statements

"Unlike triples, which are intended as a shorthand notation, RDF/XML is the normative syntax for writing RDF."

So your wasted note about RDF not being XML comes perilously close to Bill Clinton's stating "It depends what the definition of is is...".

But my main point was, how does someone get a Ph.D. these days for documenting something that is common knowledge?

Patrick Logan said...

How does one get a PhD like this? I was not on the thesis committee so I could not tell you.

I only thought the thesis worth reading, not that it was seminal.

Anonymous said...

Someone needs to think carefully about the difference between syntax and semantics. XML is the conventional, indeed "normative," syntax for writing RDF, but an RDF graph is more than just its encoding as an XML document.

That is, just because an application can parse and manipulate XML doesn't mean that it "understands" RDF. (Note that the converse is also false.)

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