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From "Alex Karasulu" <aok...@bellsouth.net>
Subject RE: [Quick Tutorial] Using RDF
Date Thu, 13 Nov 2003 14:25:15 GMT
Nick,

Any educational links would be appreciated.

Thanks,
Alex

> -----Original Message-----
> From: Niclas Hedhman [mailto:niclas@hedhman.org]
> Sent: Thursday, November 13, 2003 4:06 AM
> To: dev@avalon.apache.org
> Subject: [Quick Tutorial] Using RDF
> 
> 
> 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                        |
>  "Pär 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
> 
> 
> 
> 
> 
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