On Aug 29, 2005, at 11:24 PM, Gary Poster wrote:

On Aug 26, 2005, at 3:03 AM, Daniel Krech wrote:

On Aug 25, 2005, at 3:10 PM, Michel Pelletier wrote:

On Thu, 2005-08-25 at 14:32 -0400, Gary Poster wrote:

see what he thinks. I wonder how "lite" the component kernel can go.

The only thing I have in mind is the interface package, which is what
Twisted uses.  That's all we would need.  zope.component needs
zope.interface, zope.testing, and zope.exceptions, according to its

Right. Well in this case we would provide just a very simple interface
facade that had no effect when run in an environment with no
zope.interface (ie, catch the ImportError, null-out the facade) or hook into zope.interface if it is available. This way rdflib can be still be
used with or without zope.interface.

Sounds good.

OK, cool.

We've started a branch where we'll be depending on zope.interface and in the end may just choose to grow a dependency on zope.interface or provide some kind of fallback if possible. We're just going to concentrate on getting going with zope.interface for now.

In the mean time the adapters can live inside Zemantic, which is an
rdflib to zope bridge anyway.  Let me know if you want to send
otherwise I'll probably get around to adding functionality like this

I'm actually interested in trying to hook this up, but have very
limited time.  I might play with it just within RDFLib alone during
some hobby time tonight, but otherwise may need to toss this off to
you if you'll catch it.

I also kind of want to hear Dan's reaction before I spend too much time.

#redfoot on freenode is a good place to catch him, and me.

Yep, feel free to stop by anytime.

OK, cool, I plan to again. :-)

I thought I read that an RDF triad was itself something that could be a node in another RDF triad, but I can't find that anywhere now. Can
you confirm or deny? :-)

Yes, it's called reification, making a statement about a statement.


http://en.wikipedia.org/wiki/ Resource_Description_Framework#Statement_reification_and_context


Reification is probably best avoided. I'd recommend seeing if you can make use of a context or quoted graph instead.

I have read that 'context' actually is still a word looking for a firm definition in RDF, but I like the interpretation that it is the source of the assertion. That's not a general answer for the sorts of things that reification can provide, though.

Correct, 'context' was not a term defined in the set of RDF specifications, but all the RDF toolkits end up implementing them because pretty much all applications need them for something or another. RDFLib's support for contexts does not constrain the interpretation of what a context represents... it only provides a way to identify a set of triples. The identifier can be either a URIRef or BNode and can be used to make assertion such as the source of the triples, creation date, or whatever assertions your application wants to make about the context.

The quoted graph does seem interesting: I said before that it seems very similar to reification, and it does, but I guess it subsumes the data structure that reification can provide...I also said that I wonder about efficient indexing, and I still do.

On the plus side for context, you've implemented it. ;-)

I hope to be implementing support for quoting soon... not sure of an ETA yet.

I'm interested in contemplating RDF as a full catalog solution for Zope, at least as a thought experiment. The SPARQL work seems interesting, in regards to some of the recent discussion on the Zope 3 list; and the ability to seamlessly and simultaneously query both relationship information between objects and more traditional catalog data seems compelling.

It seems to me that allowing a back end to index particular relationships--and joins, particularly through blank nodes--would be a big step in letting RDF actually be a front end to a full catalog. Another step would be having a front end that honored rdfs range and domain constraints.

I plan to get on IRC and bother you all again as soon as I have time to do so. :-)

Hope to see you soon,


Daniel Krech, http://eikeon.com/

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