How can I implement a custom restriction based on element or attribute value.

I have the following xml

<courses>
<course id="1">
<students>25<students>
</course>
<course id="2">
<students>30<students>
</course>
</courses>

I want to define a valid value for <students> element for each course id. There can be lots of courses. Say maximum value for students in course 1 is 30.

Some elements might be required based on the value of the course id.


How do I define an xsd for these?Is it possible?

__________________
\"Dont you ever give up!\"

XSD 1.0 doesn't support this feature (known as "co-occurrence constraints"). You can do it in XSD 1.1 using assertions. However, I'm sceptical whether this is a good design: the maximum number of students on each course looks to me like data, not metadata, and I'm not sure it really belongs in a schema.

__________________
Michael Kay
http://www.saxonica.com/
Author, XSLT 2.0 and XPath 2.0 Programmer\'s Reference

mkhay,
I just used that as an example, I am really after the co-occurrence constraints.

Thank you very much..

__________________
\"Dont you ever give up!\"

You can try out assertions (and conditional type assignment, which is sometimes a better approach to the problem) using Saxon-SA 9.1

__________________
Michael Kay
http://www.saxonica.com/
Author, XSLT 2.0 and XPath 2.0 Programmer\'s Reference