RDF Identifier Terminology

Status

$Revision: 1.1 $ $Date: 2002/07/31 20:44:17 $

Just some thoughts.

Background

It seems like every RDF API defines a class (or small class hierarchy) for identifiers of things described in RDF. But the terminology varies a lot.....

What to Name this Class?

This is a difficult decision. We're handling information about lots of things. Those things are identified by instances of this class.

The first question is: should we call this class Thing-Which-Is-Pointed-To or Pointer-To-Thing? The decision here depends, in part, on how much you think about variables (a different sort of identifier), triples-centric vs node-centric APIs, having multiple pointers to a thing, bNodes, and literals.

Thing-Itself Names

These are great for blurring the line between normal objects in the program and things on the semantic web. Objects can be semweb objects, instead of being identified by identifiers.

• Thing - sounds very informal, suggests physical objects, best name DAML could come up with
• Object - the leading term in logic and programming, but it's already been borrowed from linguistics by the RDF community with a different meaning (arrrrrg!!!)
• Resource - this is what the Web community sometimes calls things
• SharedObject

Pointer-To-Thing Names

These are great for staying explicit about the referencing and derefencing which is really going on. They do make some simple operations more complicated, because you need the explicit dereference. Do these things need to be variables, too? Or is that some other class? Maybe "Reference" allows both kinds, or something?

• RDFNode - It's what Jena and others use, but it's misleading since this also identifies arcs!
• Identifier - a bit long
• Ident - more ambiguous, but also more distinctive (helps distinguish between "identifier" and "Identifier", when speaking, if you want that)
• Id - even more (EricP uses RdfID)
• Symbol - The term from logic, nicely convering both Constants and (quantified) Variables
• Constant - another term from logic; all the RDF identifiers are "constant" symbols
• Handle - has a nice sense of being attached sometimes
• Name
• Pointer
• Reference

Conclusion

Personally I lean towards Ident, if I have to pick one.

Sandro Hawke
First: 2002-03-29; This: $Id: Overview.html,v 1.1 2002/07/31 20:44:17 sandro Exp $