[Dev] RDF vs Python Objects

Curt Hibbs curt at hibbs.com
Tue Nov 26 20:01:55 PST 2002


David McCusker wrote:
>
> Katie, Morgen, and I had a meeting to go other the plan for general
> interaction between Python objects and RDF, and objects and RDFS
> (for RDF schemas).  I was going to write something vague, but now
> I can write something more specific after I draw an image I can post
> on a web page for reference.
>
> The general situation is this.  Python is _really_ dynamic.  We can
> generate Python objects from RDFS and vice versa.  When we import
> RDFS, we can load the corresponding .py files (if any) to get the
> app writers preferred implementation when one exists.  And if no
> .py version is found, we can generate classes at runtime instead.

Yes, yes, yes -- this is what dynamic languages like Python are really good
at.

> And when the .py files are missing things present in the RDFS schemas,
> we can add the parts missing from the Python code.  Actual conflicts
> between RDFS and Python code can be reported as warnings when running
> under development mode.  (We should not bother end users with conflicts
> other than perhaps notes in a processing log.)

So missing parts would be generated with a "standard" api (like getters and
setters)?

> The import from RDF and RDFS to Python will be mediated by Python
> objects with some interface to be designed (real soon now), and the
> export from Python to RDF and RDFS will by mediated by other Python
> objects in the other direction.
>
> Import from RDF for data implies a SAX parser for streaming, so no
> arbitrarily large DOM structure lives in memory before import of
> data can execute.
>
> The opposite direction from Python to RDF probably involves another
> streaming interface of some kind.  (What is the general stream API
> in Python which is satisfied by files, sockets, and in-memory buffers?)
>
> Import from RDFS to create schema objects can create an in-memory
> data structure (either DOM or some friendly native Python form),
> because schemas will not generally be so large that a stream parse
> with a SAX parser is needed.

This sounds good. Are any of the RDFS that are currently contemplated
complicated enough that it should actually generate a composite object
acting as a container for smaller objects?

> I'll write more after I draw a diagram.
>
> --David McCusker
>
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