Repeating attribute specifications

[Peter Murray-Rust]

In message <011290D45A8ACF119B8B00805FD471D60344E247 at RED-24-MSG.dns.microsoft.com> David Schach writes:
> I think Tim misunderstood your question.  In the XML DTD, it is legal to
> have multiple AttistDecl's for a given element type (see section 3.3).
> This doesn't change the validity constraint of section 3.1.  Attributes
> in tags have to be unique.

I think I have misunderstood the answers as well :-)  I'd be grateful for a 
very simple explanation.

I assumed that the multiple attributes was so that if (say) 

<!ATTLIST FOO BAR CDATA "BAZ">

occurs in the external DTD and

<!ATTLIST FOO BAR CDATA "XYZZY">

occurs in the internal subset
then this is now legal whereas it wasn't before.  But what is now the default
value of BAR? I assumed it was the later declaration ("XYZZY").  Please
disabuse me if this is wrong.  [I assume that 

<FOO BAR="abc" BAR="xyz">

is illegal, still.  If not we have some software to rewrite.]

	P.


> 
> > -----Original Message-----
> > From:	Richard Light [SMTP:richard at light.demon.co.uk]
> > Sent:	Thursday, June 12, 1997 1:19 AM
> > To:	xml-dev at ic.ac.uk
> > Subject:	Re: Repeating attribute specifications
> > 
> > In message <3.0.32.19970611161725.00b540ac at pop.intergate.bc.ca>, Tim
> > Bray <tbray at textuality.com> writes
> > >>Is there anything in the XML spec which corresponds to the SGML
> > >>stricture that "there can only be one attribute specification for
> > each
> > >>attribute definition", i.e. that you can't have repeated attribute
> > >>specifications within a single start-tag?  
> > >
> > >No.  This is legal in XML.  And in SGML, with the recent TC. -T.
> >  
> > The other answer I got to this question quoted the XML Lang spec
> > (section 3.1):
> > 
> > "Validity constraint - Unique Att Spec:
> > No attribute may appear more than once in the same start-tag."
> > 
> > This seemed to deal with the issue pretty conclusively: I had just
> > failed to look under "start-tags" while thinking about attributes ;-)
> > 
> > Is this all about to change with the 30 June update?
> > 
> > Richard Light
> > SGML and Museum Information Consultancy
> > richard at light.demon.co.uk
> > 3 Midfields Walk 
> > Burgess Hill
> > West Sussex RH15 8JA
> > U.K.
> > tel. (44) 1444 232067
> > 
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> 

-- 
Peter Murray-Rust, domestic net connection
Virtual School of Molecular Sciences
http://www.vsms.nottingham.ac.uk/

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