How to define an empty or type-safe element in XSD

[SW]

Hello,

Can anyone show me how to define in an XSD schema that an element in
an XML document can either contain no text, or if it does contain text
that the text has to be of a specific type.

For example, I would like both the following to be valid, where any
text present should equate to an integer, but an empty element is also
valid:

<mytest></mytest>

or

<mytest>123</mytest>

Many thanks in advance

 

[Patrick TJ McPhee]

% For example, I would like both the following to be valid, where any
% text present should equate to an integer, but an empty element is also
% valid:
%
% <mytest></mytest>
%
% or
%
% <mytest>123</mytest>

I was waiting to see if someone who's more of a schema person than me
answered, but I'll stoke the fire by suggesting you use a union.

<xs:element name='mytest'>
<xs:simpleType>
<xs:union>
<xs:simpleType>
<xs:restriction base="xs:integer"/>
</xs:simpleType>
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:length value="0"/>
</xs:restriction>
</xs:simpleType>
</xs:union>
</xs:simpleType>
</xs:element>