[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] RE: About OWL syntax
Hi John, John said: That is intentional in the RDF Schema design: properties are a primitive notion distinct from classes. This allows you to add your own properties to existing classes. For example, you might define the class your:book, with properties dc:title, dc:author, isbn:isbn, and your:rating, the last representing what you think of the book. I could then add new properties to the class such as my:rating or my:criticizesW3C. This is part of the support machinery for the design principle "anyone can say anything about anything in RDF". -- Didier replies: I can also bring on the table that an RDF instance expressed as: <rdf:description about="#myUniqueIdentifier"> <property1>value1</property1> <property2>value2</property2> <property3>value3</property3> </rdf:description> This statement is located in one file. Let's then have another RDF statement in another file: <rdf:description about="#myUniqueIdentifier"> <property4>value1</property4> </rdf:description> I don't include here scenarios where a specific property value in one file is different form the value in the other but more the case, when a new property and its associated value is specified in another file. RDF allows me to add this new "triple" to the resource and come out with the following result <rdf:description about="#myUniqueIdentifier"> <property1>value1</property1> <property2>value2</property2> <property3>value3</property3> <property4>value1</property4> </rdf:description> Now, I let you make the right inference. See, it is possible to have properties "attached" to an "instance" and still have a distributed definition. We can apply the same reasoning to classes and properties definitions. I know, editors like protégé consider properties (i.e. slots) as separate entities from classes (i.e. classes). This way of thinking percolated in RDFS (but not in RDF since this latter was based on previous languages like KIF and MCF). Object oriented languages have the advantage of real life test (i.e. programmers using it) and from usability studies (a la Ben schnederman). This is why class definitions are compact. Now translating the composition rule inherent to frames (a la RDF) into classes and property definitions and integrating what we learned with object oriented notations, we end up with something more readable and usable. Therefore the question: is it more convenient or more readable? The answer is no. PS: Off course, in last resort, we can always use the argument that an editor will hide that complexity. I would answer that it is needed since the actual language is not very usable (from the usability perspective). Cheers Didier
|
PURCHASE STYLUS STUDIO ONLINE TODAY!Purchasing Stylus Studio from our online shop is Easy, Secure and Value Priced! Download The World's Best XML IDE!Accelerate XML development with our award-winning XML IDE - Download a free trial today! Subscribe in XML format
|