Re: Catalog requirements

[John Cowan <jcowan@reutershealth.com>]

Norman Walsh wrote:

> In catalog parlance this is the SYSTEM keyword. You don't want to
> support SYSTEM? I do, I want
> 
>   <!DOCTYPE book
>     SYSTEM "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd">
> 
> to resolve to /share/doctypes/docbook/xml/docbookx.dtd on my system.

And what I want, by *not* supporting SYSTEM, is to force people who publish
DTDs to assign them public identifiers.  Which involves fixing the
FPI infrastructure.   Which is what I really care about.

In addition, there is a technical difficulty with SYSTEM vs. base URIs:
what is the base URI of a document fetched through a catalog redirection?
If it is the resultant URI (which is what happens with HTTP redirection),
then any parts of the document addressed with relative URIs must be mapped
as well, with resulting mess. If it is the original URI, there are equal
and opposite problems.

BTW, in Socats which is done first, SYSTEM mapping or PUBLIC mapping?
I had thought that SYSTEM mapping could be applied to the output of
PUBLIC mapping, but I am very likely confused....

> Consider this instance:
> 
>   <?xml version='1.0'?>
>   <doc xmlns="http://example.com/xmlns/namespace">
>     <para/>
>   </doc>
> 
> If I hand that to a processor, it might want to validate the document.
> In order to do that, it's going to have to know what schema is
> associated with that namespace. Shouldn't we provide some mechanism
> for addressing this problem?

So this is a sort of client-side CONNEG?

> The real problem, alas, is that Namespaces[1] says you can't do
> anything with that namespace name except literal comparison.

Not exactly, just that Namespaces as such doesn't prescribe anything.
RDF Schemas, for example, prescribes that you put an RDF Schema there.

> it would be
> just as valid to put a Modula-3 class library there as far as I can
> see.

It certainly would be.

-- 
There is / one art                   || John Cowan <jcowan@reutershealth.com>
no more / no less                    || http://www.reutershealth.com
to do / all things                   || http://www.ccil.org/~cowan
with art- / lessness                 \\ -- Piet Hein