RE: Namespaces, schemas, Simon's filters.

["Fuchs, Matthew" <matthew.fuchs@commerceone.com>]

Richard,

> -----Original Message-----
> From: Richard Tobin [mailto:richard@cogsci.ed.ac.uk]
> Sent: Tuesday, August 21, 2001 3:45 PM
> To: tbray@textuality.com
> Cc: xml-dev@lists.xml.org
> Subject: Re: Namespaces, schemas, Simon's filters.
> 
> 
> >OK, I think I get it.  Local element types allow the <line>
> >element to have different validation rules depending on 
> >whether it's a child of <matt:music>, <matt:graphics> or 
> ><matt:text>.  Clearly something that DTD's can't do but is 
> >desirable.
> 
> >I have a question.  With schemas, can I arrange for the
> ><matt:line> (note it's in a namespace) element to be validated 
> >differently depending on whether it's a child of <matt:music>, 
> ><matt:graphics> or <matt:text>?  -Tim
> 
> Yes, these are exactly the two cases we're arguing about.  A local
> element declaration inside the type of matt:music
> 
>   <element name="line" form="unqualified"> ...
> 
> locally declares the element line (in no namespace), whereas
> 
>   <element name="line" form="qualified"> ...
> 
> locally declares the element matt:line.  The default value for "form"
> can be set with the elementFormDefault attribute, and the default
> default is unqualified.  The same goes for attributes, where (in my
> opinion) unqualified is a lot more natural.
> 
> There are two points in dispute: whether local elements are good at
> all, and whether unqualified ones are (no doubt there is also a view
> that *only* unqualified ones are good, but I haven't noticed anyone
> arguing that).

Actually, while I've argued as to why making local elements unqualified is a
good thing from the point of view of what local elements are, no one has
given a similar argument for why local elements should be qualified.  The
arguments in favor of qualifying them have been simply "I don't like
unqualified elements because I can't use the namespace to uniquely identify
the element" - when namespaces fail to uniquely identify different local
elements anyway.  Or they've been "I don't like local elements, and I
especially don't want them to be unqualified", which scarcely grapples with
what a local element is.  I would like to see an argument as to why they
should be qualified from first principles as I've argued for them to be
unqualfied.  

Matthew