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Re: Reification - whats best practice?

From: Jeen Broekstra <jeen@aduna.biz>
Date: Thu, 26 Aug 2004 10:48:33 +0200
Message-ID: <412DA3E1.2030805@aduna.biz>
To: Leo Sauermann <leo@gnowsis.com>
Cc: Eric Jain <Eric.Jain@isb-sib.ch>, Bob MacGregor <macgregor@isi.edu>, 'RDF interesting groupe' <www-rdf-interest@w3.org>, danbri@w3.org


Leo Sauermann wrote:

[snip]

> *I think about joining DAWG :-)
> *I want real life examples and real live RDF that fits real life use cases.
> 
>> Bob: As you noted, storage space explodes. 
> 
> 
> Eric: >Only if implemented naively. Not much extra space is needed if 
> reification is implemented by adding an identifier column to the 
> statement table.
> 
> My email was about RDF/XML as storage space. No statement table. When I 
> deploy real live applications, Idon't want to move my customers into 
> installing some RDF storage system or cumbersome embedded database. 
> RDF/XML should be fine. This is also for compability reasons.

Drifting from the topic a bit perhaps, but using an RDF store for your 
persistency does not immediately mean that you have to force the user 
to install a DBMS or anything like that. There's several triple stores 
that have their own native persistency format and that can just be 
bundled with your product as a library, requiring no extra user effort 
for installation. Advantages of such a persistent system over 'just' 
RDF/XML are:

  - more efficient storage and retrieval times (indexes, trees, etc.
    vs. XML parsing)
  - lower memory footprint
  - lower storage footprint (XML is rather verbose, as you may be
    aware)

Also, if you want quads you'll have to use a triple store anyway, 
since the RDF/XML format itself has no support for it.

> BTW Real life:
> 99% of all this Reification will be used to state things like:
> - When was this triple added to the store? (date)
> - By Whom ? (chown leo)
> - who has access rights (chmod 777) to it?
> 
> this is metadata you will see in any store that is shared by one than 
> more person (f.e. in a company environment, to use RDF as an 
> organisational memory)

You might want to take a look at the OMM extensions to Sesame 
(http://www.ontotext.com/omm), which offer precisely such 
functionality (although currently only on a DBMS-based store).

> and these will be masses of triples and masses of reification/context.

Then I'd say that using RDF/XML is not even a realistic option, not as 
your persistency format, unless you are prepared to stick a lot of RAM 
in your machine.

Jeen
-- 
Jeen Broekstra          Aduna BV
Knowledge Engineer      Julianaplein 14b, 3817 CS Amersfoort
http://aduna.biz        The Netherlands
tel. +31(0)33 46599877  fax. +31(0)33 46599877
Received on Thursday, 26 August 2004 08:47:10 UTC

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