Why do we talk in Word

Why are all internal communications in either email or Word?

Classes Vs Individuals

OK, first stumbling block when trying to create an ontology. When should I model something as a Class and when should I model it as an Individual??

In general Classes describe a concept and an Individual fulfills that description. In other words the individual or instance is the realization of the concept described by the class.

Now, maybe it's just cause I am used to it, but in programming this is easy to comprehend as there is a very clear distinction between a Class and an instance of that class (or object). However I must say this distinction is not as obvious in OWL.

For the moment I am going with this general rule of thumb. If the "thing" is going to be either the subject or object in a triple than it will be an Individual. What that "thing" is, well that will have to be the Class.

Creating a Blogging Ontology - Part 1

Ok, well long time without a post but hopefully this is the start of something now. The goal at the moment is to create an ontology specifically for blogging. It is going to mostly consist of terms defined by SIOC, FOAF and Dublin Core. In fact at this moment I'm not even sure if I will need additional terms or if there will be enough in those three.

Once that's done the next step is to codify it up, I'm using JENA which already has DC and FOAF support so just have to add a few things myself there. After that I'll post again to see how things are.

My FOAF Profile

I stumbled across Mark Birbeck's blog which has a nice article on how to create a FOAF profile which I of course had to try out. So now this is me :)

OWL

OWL (because WOL wasn't good enough) stands for Web Ontology Language. As it says on the tin this is a language for expressing ontologies. Simply put an ontology is a representation of terms (things) and their interrelationships.

OWL is a revision of the DAML + OIL web ontology language. The documentation on OWL on the w3c website is, like RDF broken down into 6 documents:

• OWL Overview
• OWL Guide
• OWL Reference
• OWL Semantics and Abstract Syntax
• OWL Web Ontology Language Test cases
• OWL Use Cases and Requirements

OWL is actually available in three sublanguages, each one an extension of the previous one.

• OWL Lite classification hierarchy and simple constraints
• OWL DL maximum expressiveness while retaining computational completeness
• OWL Full maximum expressiveness and syntactic freedom of RDF with no computational guarantees

OWL Lite ontology is an OWL DL ontology is an OWL Full ontology
OWL Lite conclusion is an OWL DL conclusion is an OWL Full conclusion

The Overview provides an introduction as well as a description of each of the OWL Schema features. The Guide then provides an extended example which is a useful read to get the concepts down.

Well it was a while since I last posted so keeping this one short so I don't put myself off posting some more so that's it for now.

RDF

RDF seems like as good a place to start as any. RDF is explained in terms of subjects, objects and predicates. Predicates link objects to subjects where the subject is the thing, the object is the value and the predicate is the property. However objects can also be subjects so to me it seems easier to think of RDF consisting of two items, objects and predicates where predicates link objects to each other. Forget this notion of subjects altogether.

An RDF graph then is the structure created when one tries to visualize a set of connected objects. There are a number of different ways to represent this graph, one is to draw it, another it to use what are called tuples (just specially formatted pieces of text) and finally one can use XML. RDF/XML is the standard way of representing an RDF graph in XML.

We that's all I'm going to say for now. On the W3C website there are a series of 6 articles describing RDF. For anyone interested in RDF but without much knowledge already I recommend you read at least section 1 and 2 of the Primer.

Of course you could just google this but the six documents in the series are:
Primer
Concepts
Syntax
Semantics
Vocabulary
Test Cases

The wikipedia entry is also worth a read although it makes a lot more sense after the Primer.

Introductions aside, let's move right along

Ok, some reading first.

W3C Semantic Web Activity is a good place to start to gain some insight into what the semantic web is. It provides the RDF (Resource Description Language), OWL (Web Online Ontology Language) and SPARQL (RDF Query Language) specifications and has some interesting links in it's Publications section, including a recent interview with Sir Tim Berners-Lee about the Semantic Web (although I found the sound quality made it quite difficult to listen to).

So looks like there's already a lot to read, I wonder how much of this website is semantically described?