Hi, gang... Went through a crash course in RDF (10minutes), and would like to share the initial impression.
RDF is NOT XML!!! It can be represented in XML, and I'll get to that. RDF is about making simple statements about a resource. The statements are thought or primarily represented as TREEs. The arrowed lines between the nodes in the tree are the Predicates. The node at the start of the line is the Subject, and at the end is the Object. +---------+ Predicate +--------+ | Subject |------------->| Object | +---------+ +--------+ also known as a "Triple". For instance, I could say; http://niclas.hedhman.org/repository is owned by Niclas Hedhman In this case, "http://niclas.hedhman.org/repository"; is the subject, "is owned by" is the predicate and "Niclas Hedhman" is the object. But RDF is smart to say that each element in the "Triple" is a URI reference, so it can look like this; +-------------------------------------+ |http://niclas.hedhman.org/repository | +-------------------------------------+ | | http://hedhman.org/semantics/owned | V "Niclas Hedhman" "Niclas Hedhman" is string literals, and that is allowed, but by having another URI reference there we could increasing the knowledge about the owner. +-------------------------------------+ |http://niclas.hedhman.org/repository | +-------------------------------------+ | | http://hedhman.org/semantics/owned | V +-----------------------------------+ |http://hedhman.org/family/640925-1 | +-----------------------------------+ | | | http://hedhman.org/semantics/fullname | | V | "P�r Niclas Hedhman" | | http://hedhman.org/semantics/birthdate | V "1964-09-25" And so on. RDF allows the use of prefixes, just like XML, to reduce the verbosity and improve human readability. Let's take a quick look at how the above could be represented in XML. <?xml version="1.0"?> <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"; xmlns:hed="http://hedhman.org/semantics"; > <rdf:Description rdf:about="http://niclas.hedhman.org/repository";> <hed:owned rdf:resource="http://hedhman.org/family/640925-1"; /> </rdf:Description> <rdf:Description rdf:about="http://hedhman.org/family/640925-1"; > <hed:fullname>Niclas Hedhman</hed:fullname> <hed:birthdate>1964-09-25</hed:birtdate> </rdf:Description> </rdf:RDF> RDF also supports user definable datatypes and containers (collections, sets), but I won't touch on that here. An RDF schema is a description on how the statement elements can be formed together. There is a declarative language for that, RDF Vocabulary Description Language. It may at first feel a bit awkward that RDF is used to define the schema language, i.e. RDF is used to describe your RDF. (But so is XML Schema). It supports quite a lot of object-oriented concepts, including subclassing, so it is easy to understand, but I won't go into details here. So let's get on with it ;o) Niclas --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
