From: Arjun Ray <aray@nmds.com.invalid>
Newsgroups: comp.text.sgml
Subject: Data attributes: Extending the basic syntax 
Date: Mon, 27 Nov 2000 02:42:02 -0500
Organization: FUDGE Dispersal Systems
Message-ID: <ap142t85r6glirbadehjpbq0p0g0936tm4@4ax.com>



Two use cases to think about:

1. Before Annex K, only in an external entity declaration could one
associate both a notation and a set of data attributes:

  <!NOTATION  foo  SYSTEM
              >
  <!ATTLIST   #NOTATION   foo
              bar    CDATA    #IMPLIED
              baz    CDATA    #IMPLIED
              >
  <!ENTITY    blort  SYSTEM   NDATA  foo [bar='flurble']
              >

Now, we can also use this mechanism (notation name + data attribute
list) to qualify the value of an attribute (K.4.4.2-3):

  <!ATTLIST   whatsit
              gizmo   DATA   foo [bar='flurble']   #IMPLIED
              >

But we still don't have a way to do this for the data content of an
element.  The basic problem appears to be syntactic: how to tell the
data attributes from the regular attributes, and perhaps, how to fit
such information into an ATTLIST declaration.


2.  There is no clean way to invoke architectural processing.  Never
mind the ArcBase or ArchUse PIs to get everything going - we probably
need something to that declarative effect in any case - there's also
the problem of architectural support attributes looking more than a
little factitious when I do something like this:

  <!NOTATION  html  PUBLIC "+//IDN w3.org//NOTATION HTML 4.0//EN" >
  <!ATTLIST   #NOTATION    html
              ArcFormA     NAME   #FIXED  "html"
              ArcNamrA     NAME   #FIXED  "htmln"
              -- etc --
              >

After all, 'ArcFormA' and 'ArcNamrA' and their kin come from the AFDR,
but somehow everyone (me, my software) has to "know" this.  What I'd
like to do is to associate those attributes with the AFDR *notation*, 

  <!NOTATION  AFDR  PUBLIC  "ISO 10744//etc etc" >
  <!ATTLIST   #NOTATION  AFDR
              ArcFormA    NAME   #IMPLIED
              ArcNamrA    NAME   #IMPLIED
              -- etc --
              >

and then use data attribute mechanism to associate an instantiation

             AFDR [ArcFormA="html" ArcNamrA="htmln"]

with something that identifies the "html notation".

    
The general point is that the syntactic form of a name plus [attspecs]
could also be profitably applied in other places.

A.  In an element declaration:

  <!ELEMENT   blort   DATA  foo [bar='flurble']
              >

which would be equivalent to a (#PCDATA) content model, except that we
also tie an attributed data content notation at the same time.  This
is exactly the same feature K.4.4.2-3 is now giving us for attribute
values only. 

B.  In a notation declaration:

  <!ENTITY    html-dtd  PUBLIC "-//W3C//DTD HTML 4.0//EN"
              >        
  <!NOTATION  html  PUBLIC "+//IDN w3.org//NOTATION HTML 4.0//EN"
                    AFDR [ArcNamrA='htmln' ArcDTD='html-dtd']
              >

C.  In a start-tag:

  <blort  foo [bar='flurble'] >

This partially solves the current problem that we can only specify a
notation name through an attribute with NOTATION declared value, but
the syntax also allows a wider interpretation.  Since the form is
clearly distinguishable from regular attribute specifications (even
when minimized), it could refer to any declared notation for purposes
defined by the application.

Thoughts?  


-- 
:ar