Some questions

Didier PH Martin martind at
Thu Dec 2 12:40:02 GMT 1999

Hi David,

David said:
Or, in programming terms, the ID is local rather than global, or in
Web terms, it is relative rather than absolute (note that RDF allows
ID as well).  That's suitable for some applications, but entirely
useless for others (it's often important to have single global
identifiers for well-known people, places, and things).

Didier reply:
But most of the RDF users  set the description element "about" attribute's
value with a URL. In fact, this is OK because the spec indicates that you
are providing a description _about_ something and the about value may be its

I discovered that using this form, is, most of the time bogus. Instead, I do
what librarian discovered. Have the classification card (i.e. description
element) to be independent of any properties. So, instead of using a
location in the description element, I use instead an ID. This mainly
because the object's location _is_ a property. So, the object's location is
indicated by a "location" property. If there is no location I do not include
a "location" property.

See, this is very different. The object, this time is a collection of
properties. The description itself is uniquely identified in a description
collection by an ID (so that, if this is needed, we can relate a description
to an other). I do not use a URL as a value for the about and I tend not to
use the about attribute but instead use the "id" attribute and include the
location as a property in the description.

So, now, the real challenge for data interchange is to agree on a particular
schema or property set. Otherwise we only exchange data with our own tools

Didier PH Martin
Email: martind at
Web Boston (
Markup 99 (
Book to come soon: XML Pro published by Wrox Press

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