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Re: Decentralized RDF Distribution

From: Libby Miller <Libby.Miller@bristol.ac.uk>
Date: Mon, 19 Feb 2001 17:00:23 +0000 (GMT)
To: Frank Manola <fmanola@mitre.org>
cc: RDF Interest <www-rdf-interest@w3.org>
Message-ID: <Pine.GSO.4.21.0102191659110.1579-100000@mail.ilrt.bris.ac.uk>

As a practical means of trying to handle these sorts of problems, we
have been modelling events as first class objects in RDF, so that all
information is explicitly contextualized by time (and source) within the
RDF model, and the information modelled is as unchanging as we can make
it.
 
e.g. instead of having an annotation object, we have an annotation event
with an input of one webpage and an output of another. The event has an
agent (a person) and a context (time) associated with it. The annotation
event at that time and place by that person is unchanging, even if
further annotations are made by the same person to the same input
document.
 
This approach means that we can be sure that the resources (events)
modelled are unchanging (they have already happened), although the
things they describe may change and there may be new information about
them at a later date, and the event may be superceded by more up-to-date
or accurate events.
 
This doesn't mean that we can assume a closed world, though.
 
Some of this work is half written up at
 
http://www.ilrt.bris.ac.uk/discovery/2001/02/imeshdb/
 
It's based on Dan Brickley's ABC work:
 
http://www.ilrt.bris.ac.uk/discovery/harmony/docs/abc/abc_draft.html
 
Libby           




On Mon, 19 Feb 2001, Frank Manola wrote:

> Inserts may have been solved as far as the simple mechanics of
> publishing them is concerned, but the semantic aspects are essentially
> the same as those of updates and deletes:  you have to deal with
> temporal (or nonmonotonic) effects:  specifically, the idea that the set
> of assertions has now changed, and that may change what you now conclude
> from the set of assertions (a subsequent email has pointed out that an
> update can be considered a combined delete-and-add operation).  The
> whole issue of transactions (in the database sense) comes in too, since
> you may want to make what is a semantically-consistent modification to
> the "database" that consists of several distinct operations (inserts,
> deletes, modifys), and want somehow to bracket that set of operations.
> 
> --Frank
> 
> Aaron Swartz wrote:
> > 
> snip
> > 
> > ***Inserts
> > 
> > Inserts (adding triples) has been already solved. To insert data to
> > the decentralized database, you simply publish it to the Web at a
> > well-known location.
> > 
> > ***Updates and Deletes
> > 
> > Updates (modifying triples) and deletes (removing triples) are more
> > difficult, and require entering an area that RDF has been afraid to
> > touch: time. Most RDF systems do not factor time into the equation, or
> > at least, they do it in a simplistic way.
> > 
> 
> -- 
> Frank Manola                   The MITRE Corporation
> 202 Burlington Road, MS A345   Bedford, MA 01730-1420
> mailto:fmanola@mitre.org       voice: 781-271-8147   FAX: 781-271-8752
> 
> 
Received on Monday, 19 February 2001 12:02:20 GMT

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