|From:||Adrian Walker <adriandwalker@xxxxxxxxx>|
|Date:||Sun, 1 Feb 2009 16:38:35 -0500|
Hi John --|
Interesting overview of Relational Databases vs RDF. You wrote:
The problem with SPARQL is that RDF is not designed to support
indexing. The people who built so-called "triple stores" say
that they're efficient because they run in RAM. But any DB that
fits in RAM is a toy. If you take a non-toy DB and map it to
RDF, it doesn't fit in RAM. Furthermore, those triples aren't
indexed, and they're not designed to be paged in an orderly
fashion. The result is endless disk thrashing.
Let me play devil's advocate for RDF for a moment.
One of the many ways of writing RDF is to take the N3 format and expand it to make all the triples explicit. (No shorthand with commas or colons.). Call this RDFe.
Now put your RDFe in a relational DBMS table, and index it in all possibly useful ways. Maybe also do some design that splits the table on classes of the second items in the triples.
Yes, applications will cause the DBMS to spend a lot of time re-assembling n-ary relations from from the explicit triples. However, it's likely that using high end hardware plus scads of memory can yield, say, perfomance similar to that of the original relational database on a laptop. And in some cases the n-ary relations can be precomputed.
Whether RDF(e) gives you functionality that's worth the above effort is of course another question.
Cheers, -- Adrian
 See e.g. www.reengineeringllc.com/demo_agents/RDFQueryLangComparison1.agent
Internet Business Logic
A Wiki and SOA Endpoint for Executable Open Vocabulary English over SQL and RDF
Online at www.reengineeringllc.com Shared use is free
On Sun, Feb 1, 2009 at 2:55 PM, John F. Sowa <sowa@xxxxxxxxxxx> wrote:
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