<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"><HTML><HEAD><META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=utf-8"></HEAD><BODY><DIV>I (we) desperately need to solve the puzzle of how to
compose (re-use) conceptual specifications. Can we create a flexible
system of base classes that can be snapped together to make useful data exchange
applications? I think this is one of, if not THE most import tasks for the
incipient TDWG Architecture group.</DIV>
<DIV> </DIV>
<DIV>So I'm trying to educate myself about RDF versus XML (and their respective
schema tools). I came across this comment on RDF versus GML, <A
href="http://www.mapbureau.com/gml/">http://www.mapbureau.com/gml/</A>, which
contained this:</DIV>
<DIV>
<P><FONT color=#ff0000><excerpt></FONT><BR>[...] GML is not directly
composable with other XML languages. Entities that are described by other
languages cannot legally play the role of geographic features in GML. This
because all types of geographic features are required to derive from the GML
abstract class <B>gml:AbstractFeatureType</B>. Even if it were not for this
formal requirement, the lack of conventions about how to represent even simple
semantic notions in XML languages would prevent effective integration of GML
with XML languages developed independently. </P>
<P>The non-composability of GML requires that it absorb as application schemas
the multitude of other domains to which geographical information is relevant.
Failing this, non-standard mechanisms of some kind must be used to relate GML
content with external data.</P>
<P>Indeed, GML positions itself as a universal, rather than geography-specific,
semantic standard by including its own general formalisms for collections,
assertion of properties (in a style very much like RDF), time and processes, and
reference between content in separate files (via Xlink). GML can be viewed as an
alternative not just to geography in RDF, but to RDF itself. <BR><FONT
color=#ff0000></excerpt></FONT></P>
<P>This seems like a problem for us because some aspects of our biodiversity
information are decidedly not spatial. Is this a problem with XML Schema
generally or just the way it was used to create GML? Several TDWGers are
getting enthusiastic about RDF, despite the cautions of McCool (referenced by
Bob Morris earlier on the TDWG-GUID list). Should we go ahead and cast
DarwinCore as a GML application while we gear up for a coordinated switch to
RDF?</P>
<P>-Stan</P></DIV></BODY></HTML>