Hi Bijan and Richard,
I think it would be helpful for this discussion to distinguish a bit between
the different use cases of Semantic Web technologies.
Looking back at the developments over the last years, I think there are two
general types of use cases:
1. Sophisticated, reasoning-focused applications which use an expressive
ontology language and which require sound formal semantics and consistent
ontologies in order to deliver their benefits to the user. In order to keep
things consistent, these applications usually only work with data from a
small set of data sources. In order to be able to apply sophisticated
reasoning mechanisms, these applications usually only work with small
datasets.
2. The general open Web use case where many information providers use
Semantic Web technologies to publish and interlink structured data on the
Web. Within this use case, the benefits for the user mainly come from the
large amounts of Web-accessible data and the ability to discover related
information from other data sources by following RDF links.
For each type of the use cases, there is usually a different set of
technologies applied. OWL and classic heavy-weight reasoning for the first
use case. HTTP, RDF, RDFS and light-weight smushing techniques for the
second use case.
In the first use case, people think in terms of "ontologies", for instance a
basic concept in OWL2 are ontologies. In the second use case, classes and
properties are mixed from different vocabularies as people see fit and are
related to each other by RDF links.
The second use case is inspired by the Web 2.0 movement and aims at
extending the web with a
data commons into which *many* people publish data.
As it is not very likely that all these people will be logicians and
understand (or are interested in) the formal semantics behind the things
they do, people (including me) working on the second use case are often a
bit critical about too tight formal semantics and extended public
discussions about minor details that arise from some specs.
These discussions have been a mayor obstacle to deploying the Semantic Web
over the last years as they drive away people away from using the
technologies. I think that the normal Web developer will never bother going
into the details of OWL (DL, 2 or whatever version). Fearing to do something
wrong and state something that was not intended, common Web developers
usually prefer not to touch these languages.
I'm personally convinced that we can do very cool things just with HTTP, RDF
and RDFS for now and I see the current developments around Semantic Web
browsers like Tabulator or Marbles, Semantic Web search engines like Sindice
or Falcons and the growing number of people publishing Linked Data on the
Web as clear indicators for this.
So why not being a bit more specific about the different use cases of the
technologies and tell data publishers that it is OK just to use RDFS and
that they do not have to care about the complicated details that arise from
the different OWL specs.
Another idea along this line would be to rename OWL2 into Ontology
Interchange Format (OIF). The Web rules language is already called Rules
Interchange Format (RIF). Looking at the current OWL2 spec, I get the
feeling that the working group designs a language for exchanging ontologies
between knowledge based systems and that requirements from use case 2 do not
play a very important role. Thus renaming the language could make the use
case more clear and could be helpful for marketing the Semantic Web to Web
developers that have understood the the benefits and limitations of
microformats and now look for a better way to publish structured data on the
Web.
Cheers
Chris
--
Chris Bizer
Freie Universität Berlin
+49 30 838 54057
[EMAIL PROTECTED]
www.bizer.de
----- Original Message -----
From: "Jens Lehmann" <[EMAIL PROTECTED]>
To: "Richard Cyganiak" <[EMAIL PROTECTED]>
Cc: "Bijan Parsia" <[EMAIL PROTECTED]>; "John Goodwin"
<[EMAIL PROTECTED]>; "Chris Wallace"
<[EMAIL PROTECTED]>; <[email protected]>; <[EMAIL PROTECTED]>
Sent: Wednesday, July 30, 2008 7:47 AM
Subject: Re: Southampton Pub data as linked open data
Hello,
Richard Cyganiak schrieb:
Bijan, Knud, Bernard, thanks for the clarification.
I'm indeed surprised! Subclassing rdfs:label is okay in RDFS, and it is
okay in OWL Full, but it is not allowed in OWL DL.
The RDF consumers I'm working on (RDF browsers and the Sindice engine)
don't care if you're in OWL DL or not, so I'm tempted to argue that it
doesn't matter much for RDF publishing on the Web. (IME, on the open
Web, trust and provenance are much larger issues than inference, and I
don't believe that the open Web will ever be OWL DL, so why bother.)
Apart from the subject of this discussion, I find such general
statements very dangerous. The fact that the tools you develop do not
require, or make use of, OWL DL isn't really a strong argument. There
are other people (like me) relying on reasoning, which is easier to
accomplish in OWL DL. Clearly, it is important to publish data even if
it does not conform to OWL DL, but that doesn't mean that we shouldn't
bother to get it "right" (hopefully in OWL 2). Also note that it is not
important for the whole open web to be in OWL DL, but only those bits of
it you need for a particular task.
Kind regards,
Jens
--
Dipl. Inf. Jens Lehmann
Department of Computer Science, University of Leipzig
Homepage: http://www.jens-lehmann.org
GPG Key: http://jens-lehmann.org/jens_lehmann.asc
