

Re: What is a semantic web application

From: Renato golin <renato@ebi.ac.uk>
Date: Thu, 06 Dec 2007 21:59:07 +0000
Message-ID: <475870AB.4050404@ebi.ac.uk>
To: Ehsan Sadeghi <ehsansad48@gmail.com>
CC: semantic-web@w3.org

Ehsan Sadeghi wrote:
> application that creates a network of logically connected data/resource 
> with any means? lets say with a database.

Dear Ehsan,

Far from being an expert, my view is that whenever you start using 
semantic data (RDF, OWL, etc) you already have a "semantic web" 
application. This is because you probably have chosen to use semantic 
data to connect things easier in the first place.

I mean, using RDF does not imply to have your data fully connected but 
ease future connections to be made at a level that is the same as having 
"2" in one side and "2" in the other you just have to put the "=" 
between them (if you want).

The big deal of RDF/XML against, lets say, XSD/XML (the 'normal' XML) is 
that RDF can use the same vocabulary for many things and even using 
different vocabularies they can be automatically merged.

In the case of the XSD/XML, if you don't use the same schema (XSD) you 
need to build one program for each conversion between two XSDs. So if 
you have three schemas you need 3 programs, 4 schemas need 6 programs 
and so on. On the other hand, the same program reads any RDF in the world.

The drawback is that RDF is so generic (to allow such marvellous 
features) that it's almost impossible to work with large sets of RDF as 
you do with relational databases. It's like having only one table with 
three fields: subject, predicate, object and using a SELECT statement to 
retrieve information from it. It's just impractical.

Some RDF engines came to help, indexing in a different way but still 
performance is the worst part of RDF and (in my humble opinion) the 
reason for RDF (much older) not being as accepted as XSD in the industry 

hope that helps,
Received on Thursday, 6 December 2007 21:59:33 UTC
