[Zope3-dev] Re: [DRAFT] local portlets and perspectives

Olivier Grisel ogrisel at nuxeo.com
Thu Aug 25 05:30:19 EDT 2005


Jean-Marc Orliaguet wrote:

> 
> (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.

In the portletInPerspective example, one would similarly need to 
introduce a primary key to be able to describe the same facts using 
bianry relations only and thus being able to use a rdflib graph to store 
and query the local/contextual porlets layouts.

--
Olivier



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