On Apr 7, 2005 7:09 PM, Michel Pelletier <[EMAIL PROTECTED]> wrote:
> On Thursday 07 April 2005 11:24 am, Michel Pelletier wrote:
> > I haven't looked at the ST library much, I get the impressions it's more
> > focused on similar uses to that of Archetype references, which is great.
> > There are features in AT refs that would be a bit clumsy to implement in
> > Zemantic (like relationships being persistent objects with behavior and
> > data) although not at all impossible.
> >
> > Clumsy unless you need your relationships to span systems and applications.
> > The your relationship model must be based on something like RDF or its
> > equivalent (something that does not apply application specifc
> > interpretation to the stored references).  The other upshot of using
> > something like RDF is that you are not inventing a whole relational model
> > that does not necessiarly play natively with others.
> I should probably be more clear by saying that I don't know if ST's package
> has these same benefits as RDF, Kapil and Ben told me it's based on an XML
> linking standard (XLink?) so it's quite possible. Kapil also pointed out to
> me that exporting one relational set onto another is, one way or the other,
> pretty straightforward if one wants to "span systems and applications".  RDF
> is just one standardized way to do this with minimal pain, and as I
> understand it there are others (topic maps, A. Water's xsdb, probably many
> more...)

I was (clumsily) working on a system that stored curriculum and
assessment data for our high school in an rdflib triple store when
SchoolTool arrived on the scene.  Since I seem to have been literally
the one person on Earth who was ecstatically excited by the idea of a
Zope 3 based directed graph model of school administrative data, it
was probably inevitable that I would end up succeeding SteveA as
SchoolTool project manager.  Regardless, this is something I've given
a lot of thought.

I haven't tried zemantic, although I've joined the mailing list.  Here
are some differences between the way SchoolTool's graph works and RDF
normally works.

* SchoolTool currently stores absolute paths, not URI's

* SchoolTool's relationship library creates pairs of relationships;
e.g., jesus -> child of -> mary AND mary -> mother of -> jesus. 
Coming from RDF, this has consistently puzzled me.

* Up close, SchoolTool's relationships are more like reified RDF than
straight triples.  Each relationship is represented by its own object
with its own path.  This is necessary for the way the REST web
services API works.

* The REST API uses XLink syntax, but I've concluded that is a good
idea.  You could do the same thing with RDF, but using RDF would imply
lots of other hairy complicated cases.  XLink doesn't tempt you to
complexify as much.

Regardless, if you're interested in RDF, you'll probably find Steve's
design to be worth the time to figure it out.  There's lots of cool
ideas in there.

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