RE: URIs, names and well known RDDL names, was: Re: Quick edit

[Jason Diamond <jason@injektilo.org>]

Hi.

> 	Right, emphasis on "whenever possible" and realize that
> http://www.w3.org/2000/10/XMLSchema may work for XSD under most conditions
> but we need to retain the flexibility to support, for example, multiple
> schemas on the same namespace URI. For example, suppose we have one schema
> for  editing and another for runtime validation. Each may need a different
> arcrole URI (or given a constant URI some other mechanism to distinguish
> between related resources).

Perhaps a more likely scenario would be multiple CSS/XSL stylesheets. In my
trial implementation of RDDL, I thought that a method returning the resource
with a specified arcrole would be useful. Since there's no restriction on
how many resources in a given RDDL directory can use the same arcrole,
however, I realized that that method would be returning some arbitrary
resource (in my case, the first one it found with a matching arcrole). How
would we be able to programmatically differentiate between the two XSD
resources in your example?

I agree with Henry that we should not be defining new names for types that
already have them. Right now xlink:role is required to be
http://www.rddl.org/#resource. It's obviously a resource--that's what RDDL
is designed to describe. I propose that we use xlink:role to describe the
type of resource being referenced. For a RDDL document containing multiple
schemas, the xlink:role could be http://www.w3.org/2000/10/XMLSchema. The
xlink:arcrole attributes should then describe the context in which those
resources (XSDs) should be used. They could be
http://www.rddl.org/arcrole.htm#edit or
http://www.rddl.org/arcrole.htm#validate or whatever URI the directory
maintainer felt was appropriate.

XLink says this about arcrole: 'For example, a resource might generically
represent a "person," but in the context of a particular arc it might have
the role of "mother" and in the context of a different arc it might have the
role of "daughter."'

(I'm actually unclear on how xlink:role is supposed to be used. XLink says:
'the role attribute indicates a property that the resource has'. Can we use
it to indicate the type a resource is? I don't see anything preventing
this.)

In your example, both resources are XML Schemas. One of those links is used
in the context of editing an instance document. The other is used for
runtime validation. They're type didn't change--just how they're used. Right
now, the resources in arcrole.htm define types. I think it should be an
error for multiple resources in the same directory to have the same
arcroles. But, it should obviously be permissable for multiple resources to
have the same types.

I'm not entirely certain that this is what RDDL is supposed to do, though.
The beauty of it was that it was simple as well as useful. Would anybody
care to draft a list of requirements that RDDL should adheed to for a first
release? To be honest, the utility it's supposed to provide keeps drifting
in and out of focus for me. If we had a succint set of goals, we might be
able to avoid ambiguities like this.

Jason.