W3C home > Mailing lists > Public > www-rdf-interest@w3.org > January 2003

Re: Use cases for Reification in RDF Triple stores

From: Seth Russell <seth@robustai.net>
Date: Sat, 04 Jan 2003 06:03:05 -0800
Message-ID: <3E16E999.6080509@robustai.net>
To: Bob MacGregor <macgregor@ISI.EDU>
CC: www-rdf-interest@w3.org

Bob MacGregor wrote:

> Our experience with Jena has exposed some glaring performance weaknesses
> in its implementation of reified statements. We hope that these problems
> will be rectified in the upcoming Jena 2.0. However, the issues that
> surface will have to be addressed by any triple store implementation.
>
> In some of our applications the truth of a statement (triple) is relative
> instead of absolute, ranked according to a probability or to a degree of
> trust. The basic processing loop retrieves all statements that match a
> particular pattern, and then sifts through the retrieved statements to
> pick out the winner according to some metric. In Jena, a reified
> statement may or may not be indexed. If its not, then our processing loop
> will not find it. Hence, for our applications ALL statements are indexed.
> In API terms, this means that all statements must contained by (added to)
> a model, whether or not they are reified, and whether or not they can be
> considered to be 'true'. Effectively, this means that the Jena 'bit' that
> records which statements have been added to a model is useless.
>
> So the first lesson is that all statements should be indexed (note:
> heavyweight KR systems -- CycL, Epikit, Epilog, SNePS, Loom, PowerLoom --
> already do this).
>
> Secondly, there should be a 'bit' that API users can use to mark
> statements as true or not. However, it really should be 'wider' than a
> single 'bit'. Give us enough bits (e.g., make it a resource), and we can
> use such an attachment to build our own context mechanisms. 

I think you're on the something here.   But what does "it" in your 
paragraph above refer to ?  Does "it" refer to a Jena Model ?   And if 
so, and we have made ~it~ is a resource, well then ~it~ should have a 
URI (if only internally), right?   But then the problem is you don't 
have a triple anymore, you got a quad.    So why not just cop to it .. 
we need quads ... not triples.  

[seeAlso
    <http://robustai.net/sailor/grammar/Quads.html>
    <http://robustai.net/mentography/mentography.html>].

Seth Russell
Received on Saturday, 4 January 2003 09:03:39 GMT

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