[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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