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   Naming ModSAX features: good use for the 'java:' URI scheme?

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  • From: Dan Brickley <Daniel.Brickley@bristol.ac.uk>
  • To: XML Developers' List <xml-dev@ic.ac.uk>
  • Date: Mon, 8 Mar 1999 22:58:03 +0000 (GMT)

On Mon, 8 Mar 1999, Tom Harding wrote:

> David Megginson wrote:
> > As I wrote before, it doesn't much matter whether we use Java property
> > names incorporating domain names (like
> > 'org.xml.sax.features.validation') or URIs (like
> > 'http://xml.org/sax/features/validation'), as long as we have the
> > ability for people to create new names without fear of collision.
> I would also urge against using an http: URI since it is not meant that a resource actually be
> retrieved using the http protocol.

I think I've found a compromise of sorts that'll let us use the Java
naming scheme (for those uncomfortable with naming conceptual entities
in the http namespace), whilst still using URIs.

>From http://www.w3.org/Addressing/schemes.html

	Addressing Schemes 
	This is (an attempt at) an exhaustive list of URI schemes. I try to list
	them all, whether they're standard or not. 

Under 'J' we find a useful looking entry...

	java:  identifies java classes (@@spec?) 

There's also a reference to a JavaRMI: URI schema invented by Bill
Jansen, which would be interesting to track down. But anyway...

So... here's the proposal:

	Naming ModSAX Features

	ModSAX is intended to be easily extensible, and is designed to
	anticipate future independently developed extensions ('features').
	For ModSAX-aware software to cope with the decentralised evolution of
	new features, it is important to have a controlled mechanism for naming
	these features unambiguously. For this we adopt the Uniform Resource
	Identifier (URI) system defined in RFC 2396[URI]. Each (version of a) ModSAX
	feature should be assigned a unique URI. It should not be assumed that 
	these identifiers can always be  dereferenced to acquire further
	information about the feature they name. 
	For example, the 'http:' scheme and 'java:' schemes can be used.
	'http://purl.org/net/sax/MyFeature' and 'java:org.desire.sax.MyFeature'
	are both legitimate names for SAX features. 'phone:+44-117-9287493'
	would not be an appropriate name, since the 'phone:' URI namespace can
	only be used for telephone numbers. 

This way, people who manage http: URI names and want to use them to name
SAX features are free to do so. Others can piggyback on the DNS via the
java: scheme instead. But both through the same overarching approach.

So... It would be nice to have a reference to some spec defining the 'java:'
URI scheme mentioned at http://www.w3.org/Addressing/schemes.html
Maybe somebody from Sun has a pointer to this...?

BTW as a side effect of having a URI scheme for Java classes and
intefaces, we can exchange (aggregate, search, reason over) RDF
metadata about those resources. This would be handy in Sun's JINI
amongst other places.... Here's a quick and dull example of metadata
keyed off a java: URI...

	<rdf:Description rdf:about="java:org.desire.rudolf.jtree.NavApplet">
	<dc:Creator>Dan Brickley and Larry Franklin</dc:Creator>
	<dc:Description>This applet is an attempt at a metadata browsing tree control</dc:Description>
	<rdfs:seeAlso rdf:resource="../moremetadata.rdf"/>

But I'm sidetracking again. I'm really just saying one thing: the
existence of a URI schema for Java classes (and packages) means we don't
need to choose between Java and URI naming formalisms. We can have the
best of both worlds...


[URI] Uniform Resource Identifiers (URI): Generic Syntax; Berners-Lee,  
Fielding, Masinter, Internet Draft Standard August, 1998; RFC2396. 

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