RE: URN as namespace URI for RDF Schema (run away... run away... ;-)

  

For schemas I would strongly recommend not to use urns and instead use normal http urls.

definition social practice: 
>90% of people do it.
if you stick to it, it helps to make things look familiar when we use your schemes.
do not write your schemes by looking at the specs.
write them by copying from 
http://www.schemaweb.info
  
 

think of the story of the www: everybody knew how to do HTML because we all copied the source of everybody else ;-)


 
Agreed. 
 
But be very careful to ignore all those schemas which use URIrefs
with fragment identifiers to denote vocabulary terms, including
the official RDF schemas for RDF, RDFS, OWL, etc... ;-) ;-) ;-)
 
Particularly good example schemas to emulate [1] are:
 
 <http://sw.nokia.com/schemas/general/VOC-1.0.rdf> http://sw.nokia.com/schemas/general/VOC-1.0.rdf 
 <http://sw.nokia.com/schemas/nokia/FN-1.2.rdf> http://sw.nokia.com/schemas/nokia/FN-1.2.rdf 
 <http://sw.nokia.com/schemas/nokia/MARS-3.1.rdf> http://sw.nokia.com/schemas/nokia/MARS-3.1.rdf 
 
Note the use of the VOC-1 vocabulary to define functionally
significant sets of terms, including the ability to group
terms by subvocabularies, which fully alleviates the need
to pay any attentions whatsoever to any syntactic features
employed by the RDF/XML serialization, namely XML namespaces.
 
Also, note the benefit of using http: URIs (not URIrefs
with fragment identifiers) to denote your vocabulary
terms per the following real-world examples:
 
--
 
Feel free to resolve (HTTP GET) any of the following
terms for a human friendly representation (with hypertext
links to other human friendly representations of related
terms to boot!):
 
http://sw.nokia.com/VOC-1/Vocabulary
http://sw.nokia.com/FN-1/topic
http://sw.nokia.com/MARS-3/relevance
 
If you want something machine readable, consider using
URIQA [2] (HTTP MGET) to ask for a concise bounded 
description [3] of these terms:
 
curl -X MGET " http://sw.nokia.com/VOC-1/Vocabulary" 
curl -X MGET " http://sw.nokia.com/FN-1/topic"
 <http://sw.nokia.com/MARS-3/relevance> curl -X MGET "http://sw.nokia.com/MARS-3/relevance"
 
--
 
If you use URNs (or URIrefs with fragment identifiers), making
such representations/descriptions of your terms web accessible
(as in the examples above) becomes much more difficult and expensive. 
 
Even if you aren't sure if you will ever publish any representations
and/or descriptions for your terms, using http: URIs will give you 
that option later, without impact to any existing usage of those terms.
 
It is *not* wrong to create http: URIs which do not (yet)
resolve to a representation (no matter what AWWW [4] might be
taken to imply ;-)
 
And if you need a stable "web home" for your vocabularies,
consider utilizing the services of http://purl.org or the like.
 
Regards,
 
Patrick
 
 
[1] obviously reflecting a severly biased opinion ;-) ;-) ;-)
[2] http://swdev.nokia.com/uriqa/URIQA.html
[3] http://swdev.nokia.com/uriqa/CBD.html
[4] http://www.w3.org/TR/webarch/