Is XDEV useful? (was re: XDEV proposals)

David Megginson ak117 at
Sat Nov 22 19:09:49 GMT 1997

Peter Murray-Rust writes:

 > Thanks very much David,
 > 	You pose - but do not answer - a question :-). 

Perhaps as I move into my mid-30's I'm assuming the modesty and
humility of old age (though those who have endured a conversation with
me may have their doubts).

 > >Whenever your processing software finds an external data entity with
 > >the XML notation, it can simply call the parser recursively.
 > This is very clever! Thanks for pointing this out. I wouldn't have thought
 > of it. 
 > It does, however, require that each ENTITY consistently uses just one DTD.

Each entity can have its own DOCTYPE declaration -- simply start a new
invocation of your parser.

 > I have read - and appreciated this. I think that, without having an
 > AF-aware processor to hand, and a friendly guru, it's too difficult for
 > *me*. And certainly for my community. But I know there are a lot of
 > devotees of AFs on this list, and perhaps they can come to a communal view
 > as to whether there is agreement as to how they are to be used in XML and
 > what software is required (because they do need software).

The simplest approach to AF does not require an architectural engine
at all; instead, simply look at attribute values instead of element
type names; i.e., instead of

  IF element_name = "FOO" DO


  IF attribute_name("MYARCH") = "FOO" DO

 > > > - I wish to be able to send hypermedia. XLL specifically declines to add
 > > > any semantics to the syntax, other than an (implied) HTML-like behaviour
 > > > for some of the SIMPLE links.
 > >
 > >Are notations not suitable for specifying this information?
 > I don't know :-). I have never used NOTATION. Seeing your example above
 > suggested that it may be useful. Maybe it will add type information to the
 > thing pointed at?

That exactly its purpose -- the notation informs the processing
software of a binary entity's type:

   "+//ISBN 0-201-18127-4::Adobe//NOTATION PostScript Language
    Ref. Manual//EN"

(I have to admit that I have no idea with to do with system
identifiers for notations in XML -- in full SGML, I just leave them


 > >Here, again, architectural forms will help.  As long as you use a DTD,
 > >and the DTD implements a "food information" base architecture, the
 > >supermarket will be able to incorporate your molecular information
 > >automatically.
 > Ah - but this is the problem. I have no idea who will use my information
 > and that is why I think that AFs are limited in my area. In Java classes,
 > for example, I can use the Date class without the authors knowing I exist.
 > I hope that others can use my Molecule class/element in the same way. 

How could they possibly use your information automatically if you
weren't using some kind of shared standard?  How would they know what
information applied to what food, for example, unless you had somehow
encoded that information in advance for them?

All the best, and thanks for an interesting discussion,


David Megginson                 ak117 at
Microstar Software Ltd.         dmeggins at

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