RE: Divide the problem

Dan Connolly wrote:

> > Because "identify" to me means "names", and it does not mean
> "is identical
> > to".
>
> I agree; I did not use identify/name to mean "is identical to".

So I conclude that the string (using URI syntax) that one picks as namespace
name is just a unique point in the space of possible namespace names --
which is separate from the space of URIs.

> > Just because I pick a URI as a namespace name doesn't make namespace
> > identical to what the URI stands for.
>
> It seems to me that it does. I am at a loss for words to clarify...
> can we switch from English to the language of logic/math?
>
> The URI spec (http://www.ietf.org/rfc/rfc2396.txt)
> essentially establishes
> 	identifies: URI -> Resource
> so that "The URI i identifies the resource r" can be written
> 	identifies(i) = r
>
> OK so far?
>
> Then, looking at "I pick a URI as a namespace name" ... let's
> call that URI i1, so that "what the URI stands for"
> can be written
> 	identifies(i1)
>
> Let's call "the namespace" n1. Then you're saying
> that it's not necessarily the case that
> 	identifies(i1) = n
>
> That means there's some other function
> 	namespace-named-by: URI -> Namespace
> so that
> 	namespace-named-by(i) = n
> but
> 	namespace-named-by(i) != identifies(i)

Thanks for writing it down for me. The formal notation certainly makes it
easier to follow.

> That's a logically coherent viewpoint, but at the
> cost of introducing this distinct
> namespace-named-by function, which has not
> been necessary for any of the previous
> specs (HTML, HTTP, URIs, ...) and doesn't
> seem necessary now.

I think this distinction is necessary because of the wording of the
namespace rec. A namespace is a collection of names which share the same
namespace name. Nothing else is said about what it contains.

If we say that the namespace itself and (for instance) a schema are the same
thing because they are identified by the same URI, we end up in a situation
that sometimes a namespace is just an abstract collection of names
(xmlns="http://does-not-exist.net" returning nothing), a schema document
(xmlns="http://www.w3.org/XML/1998/namespace" returning a schema document)
or a human-readable documentation
(xmlns="http://www.w3.org/1999/XSL/Transform").

> Up to the namespace spec, there's been just one
> thing that each URI identifies in the Web.
> That is, there has been just one Web.
> It's logically coherent to consider splitting
> the Web between Namespaces
> and Everything Else, but I find it hard
> to imagine why anybody would want to do that.

I think it's unavoidable unless we define a document format that actually
describes the namespace, and put *that* at the given URI. Note that this
couldn't be a schema, because a schema is not a namespace.

> Everything else has fit into the Web of
> Resources: text documents, images, objects
> with methods, mailboxes, mail messages,
> concepts identified by UUID or OID, and
> on and on. Why splinter Namespaces out
> from this space?

I certainly did not say that a namespace should not have an identity in web
space, I just claim that using the namespace name as it is would mean to
overload it. We just might need an additional attribute (for a fresh start).

> > Sure, but I would argue that http://www.w3.org is not
> necessarily the right
> > place to do experiments like that. If it can't be avoided, I would still
> > prefer that the schema document returned actually comes with a statement
> > that this is just experimental usage of namespaces / schema.
>
> Fair enough.

Thanks.

Received on Friday, 9 June 2000 07:00:24 UTC