Is this possible using XML Schema

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Hallo,

Can the following XML structure be defined in XML Schema:

I have a set of action elements, each action has a criteria sub-element with a time attribute, and a parameter sub-element.
The parameter sub-element attributes are limited to a defined set for each action, i.e. the attributes for action1 might be:
volume="2"
or
height="1" length="4" depth="3"
for action2 the attributes might be:
span="12"
or blank


<action1>
<criteria time="2">
<parameter attributes>
<action3>
<criteria time="10">
<parameter attributes>
<action1>
<criteria time="20">
<parameter attributes>
<anotheraction>
<criteria time="10">
<parameter attributes>
<anotheraction>
<criteria time="10">
<parameter attributes>
<anotheraction>
<criteria time="10">
<parameter attributes>
<smallaction>
<criteria time="10">
<parameter attributes>
<action1>
<criteria time="102">
<parameter attributes>
<action1>
<criteria time="12">
<parameter attributes>

I want to be able to define it so that only allowed combinations of parameter attributes are allowed.

Hopefully that's explained it well enough. I'm afraid I'm new to this.

- Pete