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Feature
Storing RDF/XML in a Relational Database, Part 2
Issue: 3.3 (January/February 2005)
Author: Mark Choate
Author Bio: Mark Choate is an author and consultant residing in Raleigh, North Carolina.
Article Description: No description available.
Article Length (in bytes): 28,723
Starting Page Number: 20
RBD Number: 3311
Resource File(s):
3311.sit Updated: Wednesday, January 19, 2005 at 12:03 PM
Related Web Link(s):
http://www.schemaweb.info
http://www.w3.org/2000/01/rdf-schema#
http://www.w3.org/1999/02/22-rdf-syntax-ns#
http://paradigmasoft.com
Known Limitations: None
Excerpt of article text...
This is the second of a two-part article that describes the classes I developed to assist me with some tricky validation problems I encountered while developing an RDF schema editor.
RDF Schema
I discussed RDF in detail in the previous article, so I won't take the time to do so now. RDF is most commonly used for documenting document metadata in order to make collections of documents easier to sort and search through. What is important to remember is that RDF is comprised of statements and each statement has a subject, a predicate, and an object. A "subject" refers to what's known as a resource, which is basically anything that can be referred to with a URI. More often than not, the subject points to a web address and the predicate describes some attribute of the document at that address. The easiest way to think about this is to think of the predicate as a property and an object as the value for that property.
One of the basic rules of RDF is that predicates have to be documented in a schema, and this schema describes how and when a predicate can be used. Since I was writing a schema editor, I needed to be able to insure that the user was entering a predicate that had been predefined and that the predicate had the right value (object) and was applied to the right kind of subject. The rest of this article focuses on the classes I developed to help make this easier.
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