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RDF typed node implementation experience

From: Janne Saarela <janne.saarela@profium.com>
Date: Thu, 10 Oct 2002 16:25:30 +0300
Message-ID: <3DA57FCA.4030005@profium.com>
To: www-rdf-comments@w3.org

Hi all

Following this week's discussion on RDF Core WG list I
thought I share some of Profium's experience in implementing
data type support in literal nodes. In fact, I could have
cross-posted here a recent email I sent to www-mobile [1].

Out of the several options [2] discussed by the WG,
Profium Semantic Information Router (SIR) V3.0.4 [3]
implements proposal F.

Currently we encode data type information about
a literal value of a property by making the 'range'
predicate point to a URI that specifies the data type.
For example,

<rdf:Property rdf:ID="price">
   <rdfs:range rdf:resource="http://www.w3.org/2001/XMLSchema#double" />
</rdf:Property>

Profium SIR does not support all of the data types defined
by XML Schemas but only a limited subset. What remains us an
open issue is how to make 'range' pointers to user-defined
data types such as email addresses.

Profium SIR takes advantage of 'range' typed literals
in the following ways:

1. RDF schemas are used to validate incoming native RDF instance data

2. RDF schemas are used to enforce correct entry of RDF metadata
in a Web based interface. Profium SIR uses automated JavaScript
+ HTML creation from the RDF schema file.

3. schemas are used to guide the query language Profium
has developed. Our query language is called RDFQL even though it
is not related to other languages by the same name.
Just like querying of XML, RDF querying requires a parser
to provide the application layer i.e. the query engine
the data typing information. This information in turn enables
us to do advanced querying on RDF instead of plain string
matching. For example, we can look for RDF data where a date
was before 10-Oct-2002.

The implementation was straight-forward for items 1 and 2.
The query language has certainly required more work but
the starting point i.e. the PSVI of RDF has provided
us a good kick-start.

Regards,
Janne

[1] http://lists.w3.org/Archives/Public/www-mobile/2002Sep/0006.html
[2] http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2002Oct/0049.html
[3] http://www.profium.com/gb/products/sir.shtml
-- 
Janne Saarela <janne.saarela@profium.com>
Profium, Lars Sonckin kaari 12, 02600 Espoo, Finland
Tel. +358 (0)9 855 98 000 Fax. +358 (0)9 855 98 002
Mob. +358 (0)40 508 4767  Internet: http://www.profium.com
Received on Thursday, 10 October 2002 10:33:15 GMT

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