<?XDEV?> and BEHAVIOR: a meta-proposal and a proposal

Peter Murray-Rust peter at ursus.demon.co.uk
Tue Nov 18 23:01:22 GMT 1997

At 14:09 16/11/97 +1100, Rick Jelliffe wrote:
>> From: Peter Murray-Rust <peter at ursus.demon.co.uk>
>> That two attribute values for XML-LINK's BEHAVIOR attribute be recognised
>> through an XDEV PI:
>> 	BEHAVIOR="DisplayStandAlone"
>> 	BEHAVIOR="DisplayInContext"
>> That for the second option an additional attribute CONTEXTREF is required,
>> whose value is a valid URL and points to the XML element providing the
>> display context of the current element.
>> 	The actual details of display are application (and possibly stylesheet)
>> dependent.
>> </PROPOSAl>
>Another approach might be to use the name prefix XDEV: on attribute 
>values, e.g.
>	BEHAVIOUR="XDEV:DisplayStandAlone"
>and the contextref attribute you suggest, e.g.
>	BEHAVIOUR="XDEV:DisplayInContext"
	I have now realised (forgive my slow thinking) that this provides exactly
what is needed and I was too hasty in my earlier reply.

	As you say, the attribute value simply needs to be unique and the XDEV:
mechanism provides that (to a certain extent). It can even be linked to a
namespace if that is allowed when the namespace proposal is finalised.

	So, in the first proposal there is no need for PIs. Rick's suggestion
meets my needs, so it can be bolted in very easily.  The result is that an
XML-LINK-aware processor may, but need not, recognise BEHAVIOR attribute
values prefixed by XDEV, and one or more additional attributes with names
prefixed by XDEV.

	An XDEV-unaware processor will give a graceful message saying it doesn't
understand the XDEV: attribute and the BEHAVIOR value. [At present it will
say it doesn't understand *any* BEHAVIOR values except by private
negotiation, because none have been suggested. I'll write more later...]
This could be a good time for those more expert than me to suggest BEHAVIOR
values. [I have asked at regular intervals whether the XML-LINK attributes
would have suggested values (i.e. for ROLE, BEHAVIOR and more guidance on
CONTENT-ROLE, etc.) I think the current idea is to keep it semantically
neutral. That's why I'm raising it here...

	An XDEV-aware processor will be able to do lots of wonderful things with
the BEHAVIOR values...  especially when coupled to equipment...

	You are rightly concerned about the meta-proposal - I'll reply in more
detail, but say that PIs are now not an essential part of the meta-proposal
(though they may be required sometimes).  Your comments are very useful and
I will certainly make sure that I stress standard mechanisms (stylesheets,
for example) where possible. [I am trying to code them into JUMBO, but am
still trying to work out how closely they are coupled to a page-like output
or whether they can be used more generally.] I do not think that
stylesheets can do everything, although if XSL included a transformation
language that might help in some places.

	I shall not unleash the Monty Python proposal until we have addressed the
meta proposal a bit more. :-)



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

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