Sequence <was> Access Languages ...
Mark L. Fussell
fussellm at alumni.caltech.edu
Sat Nov 22 09:34:02 GMT 1997
Rick Jelliffe <ricko at allette.com.au> wrote:
> I think you miss what is perhaps *THE* most important thing that SGML
> content models represent: sequence.
> This is one of the essential distinguishing features of SGML.
> If I have
> <p>Refer also to
> <title>XML draft</title>
> </citation> for more info.</p>
> then the sequence of elements and data in to citation element
> are vitally critical. Sequence is not an artifact of formatting,
> in many cases, but as intrinsic to the data as encapsulation
> and so on.
[SNIP to possible Content Model]
> <!ELEMENT citation ( title, text, url)>
I think your example shows the opposite. There is no information change
between any of the orderings within the citation: <title><text><url> vs.
<title><url><text> vs. <url><title><text> etc. You may consider the
desired presentation and encoding order to be only the first but that
would be a view onto the information and not a property of the
information itself. You could alternatively define an attribute that
says citations look good in English in that particular order. Or maybe
the 'at' should be derived and the content model is simply:
<!ELEMENT citation ( title & url)>
This works well with your next example too:
> <!ELEMENT citation ( title, text, name, text, url )>
<!ELEMENT citation ( title & editor? & url )>
Depending on whether the editor is included or not, different text would
be generated at presentation.
The generated text could still be encoded in SGML but as separate
I am not saying sequence is unimportant, but I think SGML is overly
focused on it (from an IM perspective) because it comes from a
paper/linear background. Information is rarely linear: it is only time
that is, which has caused some media [and the humans who use them] to be
(mostly) linear also. It can be difficult to break that linear
assumption when it doesn't apply if your tools keep reinforcing it.
mark.fussell at chimu.com
i ChiMu Corporation Architectures for Information
h M info at chimu.com Object-Oriented Information Systems
C u www.chimu.com Architecture, Frameworks, and Mentoring
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