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   Re: RDF Sample, ICAO Airport Codes

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  • From: David Megginson <david@megginson.com>
  • To: xml-dev@ic.ac.uk
  • Date: Fri, 30 Jul 1999 13:47:16 -0400 (EDT)

Satya.Rao@chase.com writes:

 > The first line in RDF specification says
 > "The Resource Description Framework (RDF) is a foundation for processing
 > metadata"
 > I thought this is the major use of the RDF. For serializing the
 > entities can't we use XML?

RDF is a layer of abstraction that can be used on top of XML to
provide a better view of serialized objects.  

If lots of applications need to process serialized objects, it doesn't
make sense to force them all to do fairly low-level XML handling:
applications for data exchange will usually care about entities
(objects) and their attributes and relationships (properties), not
about elements, attributes, and character data.

By way of illustration, here are the major layers involved in one
particular (imaginary) process:

1. UTF-8 encoding - specifies the actual character encoding used in a
2. Unicode - specifies the abstract character points available,
         without requiring specific knowledge of the character
         encoding used.
3. XML - specifies a serialized version of a tree with typed nodes,
         without requiring specific knowledge of the characters used.
4. RDF - specifies the interpretation of the tree as a series of
         entities with attributes and relationships, without requiring 
         specific knowledge of the elements and attributes used.
5. Application - processes the entities in the abstract, and builds a
         domain-specific object tree.
6. Database - stores the object tree in SQL tables.

If you make the jump straight from #3 to #6 (for example), you'll have 
to write and maintain a lot of unnecessary code.

All the best,


David Megginson                 david@megginson.com

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