a simpler document type definition language?

Jurg Wullschleger Jurg.Wullschleger at mb.luth.se
Fri Dec 10 15:44:10 GMT 1999

hi everybody.

i like the idea of SML. but i think it is not of so big importance for
"normal" programmers: if they don't like attributes, they just don't use it.

but a really important thing to every user of XML is how to specify your
fileformat. both, DTD and Schemas open you a lots of possibilities to
specify your fileformat. but they are quite complicated. and it's not easy
to write a program that validates a xml document (i think).

so, what do you guys think about a simplified document type definition

the simplest form i can think of would look something like this: (examples
in DTD syntax)
there are only 4 types of elements:

- empty elements

- elements that contain data

<!ELEMENT name2 (#PCDATA) >

- list elements

<!ELEMENT name3 (name1|name2|name3|name4)* >

- structural elements of a fixed length

<!ELEMENT name4 ((name1|name2),name3,name4,(name5|name6|name7)) >

maybe that's a bit too restrictive, but i think it is useful for a lot of
applications. and it is really easy to "validate" a document. If the user
only uses these constructs, he can be sure that the format can easily be
handled by a program. 

i defined a simple document definition language, based one the 4 basic
element types. and wrote a small xml editor that can edit xml files which
are defined in this language. at the moment, there are two formats defined:
one for the rules themseves, with an DTD export filter, and one for a subset
of the functionality of CSS, with a CSS export filter.

download the source at http://www.netmen.ch/wullschleger/xml/Simple.zip !

And let me know what you think.


Juerg Wullschleger

email: jurg at mb.luth.se

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