[Zope3-dev] Re: Zope3-dev Digest, Vol 25, Issue 37

[Michel Pelletier]

> From: Olivier Grisel <ogrisel at nuxeo.com>
> Subject: [Zope3-dev] Re: [DRAFT] local portlets and perspectives

> > 
> > (SellerURI, merchandiseURI, BuyerURI, "Sale Transaction")
> > 
> Let's rewrite this relation to a prolog equivalent fact:
> transaction(SellerURI, merchandiseURI, BuyerURI, "Sale Transaction").
> 
> There is no primary key in that relation. We could add one such as 
> TransactionURI for instance :
> 
> transaction(TransactionURI, SellerURI, merchandiseURI, BuyerURI, "Sale 
> Transaction").
> 
> In this case we could rewrite this fact without loss of information 
> using only binary relations/predicates by projecting it:
> 
> transactionSeller(transactionURI, SellerURI), 
> transactionMerchandise(transactionURI, merchandiseURI), 
> transactionBuyer(transactionURI, buyerURI), 
> transactionType(transactionURI, "Sale Transaction").
> 
> This description is then equivalent and RDF friendly. However it 
> requires the introduction of a primary key which was implicit in the 
> first description and is much more verbose.

I think the original triadic statement can be encoded with one rdf
triple + context in rdflib:

Graph.add((SellerURI, merchandiseURI, BuyerURI), TransactionURI)

Where TransactionURI is the context.  I'm still feeling that these two
models are either equivalent, or there is some property of triadic
relations that I just don't "get" yet.  This paper:
http://www.cs.indiana.edu/pub/techreports/TR606.pdf also appears (from
reading the first five pages) to state that reified RDF triples *are*
Peirce relations, which seems to make sense as they are statements about
statements, although I can't claim to really understand the guts of the
paper.

I want to reiterate to you guys that I'm not trying to be argumentative
or prove that one thing is better than the other, I take a deep interest
in these subjects and I want to know as much as possible about them.
But unfortunately I think we've strayed off the topic for this list.

-Michel