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Re: RDF storage

• To: Howard Katz <howardk@f...>
• Subject: Re: RDF storage
• From: "Chiusano Joseph" <chiusano_joseph@b...>
• Date: Mon, 17 May 2004 15:06:12 -0400
• Cc: Joshua Allen <joshuaa@m...>, John Song <sq02@k...>, Xml-dev <xml-dev@l...>
• Organization: Booz Allen Hamilton
• References: <IKEOLCDFPBBPPAHGNKKOOEIAELAA.howardk@f...>

I think you meant to refer to Joshua :)

Kind Regards,
Joe Chiusano
Booz | Allen | Hamilton
Strategy and Technology Consultants to the World

Howard Katz wrote:
> 
> I don't know if I agree with that assessment, Joseph, at least regarding
> relational tables. I haven't done much implementation work myself, other
> than munging my own XQuery engine to provide a native internal format for
> RDF triples, but my impression is that it's not that difficult to implement
> a backend store for RDF in a relational table. Each triple ultimately just
> boils down to three integer columns, which are either pointers into tables
> of indexed URIs or literal data instances. I've been looking at doing
> exactly that with my own engine: implementing an optional SQL-based backend
> as a user option, and at first glance it doesn't look that difficult.
> 
> Does anybody on the list have contrary experience? I know at least a few
> members of the RDF Data Access Working Group have implemented backends in
> SQL. I was quite intrigued to look over a few shoulders at the last
> face-to-face meeting of the group and watch people hacking away on big
> repositories in MySQL.
> 
> I agree that implementing via a native XML database doesn't buy you much,
> other that the ability to easily [expletive deleted] in RDF that's been stored as RDF/XML
> and to serialize to the same format on output. That's definitely extremely
> useful for interop. However there's too big an impedance mismatch between
> the sort of things you'd like to do with XML and with RDF to buy you much of
> value on the query side.
> 
> Best,
> Howard
> 
> > -----Original Message-----
> > From: Joshua Allen [mailto:joshuaa@m...]
> > Sent: Monday, May 17, 2004 11:12 AM
> > To: John Song; Xml-dev
> > Subject: RE:  RDF storage
> >
> >
> > >   and the arising problems? the most difference betwwen RDF
> > > and pure XML is the data model which is hierarchical tree for XML
> > >   and graph for RDF.so if storing RDF in NXD,maybe it is
> > > needed to redesign the storage model and also mapping rdf query
> > >   like RQL into XML query language like XQuery.
> > >   It seems that the most appealing thing to store RDF in NXD
> > > is that i can utilize the index and other optimizing
> >
> > You are correct; the difference in data model makes it difficult to get
> > any advantage from Xquery.  The same applies to indexing though.  The
> > idices which are supported by native XML databases are not RDF-aware.
> > However, we could make the same criticism of relational databases -- the
> > RDF data model is not at all like the relational data model; so vendors
> > have been forced to implement custom indexing and query schemes atop
> > relational engines.  Since it requires a lot of custom work either way,
> > I do not think that either relational or native-XML have a distinct
> > advantage over the other, except for the fact that relational engines
> > are more mature, and targeting relational makes it easier to port a RDF
> > engine to multiple platforms.  A native XML database would perhaps have
> > an easier time preserving the full fidelity of the input RDF documents,
> > but it is also possible for a relational-backed engine to store the
> > source RDF in a CLOB when shredding the RDF to relational tables.
> >
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-- 
Kind Regards,
Joseph Chiusano
Associate
Booz | Allen | Hamilton

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