A beginners question about substitution groups

[Steve]

Hi,

I'm currently teaching myself about XML schems at the same time as
specifying the XML document for a project I've been given to write.
(I'm new to the XML world, so progress is a little slow at the moment!)

I find myself needing to restrict an element to contain either an
integer in the range of 01 - 99 OR the value "*9". Because of the
asterisk an simple integer field is not sufficient so I suspect I need
to use a substitution group to specify that this element can either be
an integer, or a string with only one permissable value.

I'm following the XML Schema Part 0 - 3 from the w3c.org website to
indicate what is permissible in the language.

I'm a little confused about how to code up a substitution group so that
the value is either a ranged integer, or a specific string. Could
someone point me in the direction of some other documentation which is
a little more readable than the official primer, or describe to me how
it's done - I don't want some canned XML with "This will do what you
require", as I'd like to work this simple problem through myself.

Cheers.

[Priscilla Walmsley]

Hi,

You actually need a union type rather than a substitution group. The
Primer has some coverage on that:

http://www.w3.org/TR/xmlschema-0/#UnionDt

There is an example of a union type from my book (and many more schema
examples) at:

http://www.datypic.com/books/defxmls...r11.html#EX116

Hope that helps,
Priscilla

----------------------------------
Priscilla Walmsley
Author, Definitive XML Schema
Definitive XQuery
http://www.datypic.com
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[Steve]

Aha! A union (which I'd not actually read about yet) is definitely the
way to go. I think that I may do well with a comfortable book, rather
than the precise, but slightly terse, standards docs!

Seeing as you've written both, it I feel I should look no further! :)

Many thanks Priscilla - my schema is rolling again...

Steve.