Need help with schema validation

[admin]

Hi,
I need help with xml schema.

My input xml : <sample>
<symbol>
</sample>

xsd for element: it can contain 'A', 'B' or ' '. It cannot be empty.

I tried <element name="symbol">
<simpletype>
<restriction base="string">
<enumeration value=http://www.webdeveloper.com/forum/archive/index.php/"A"/>
<enumeration value="b"/>
<enumeration value=" "/>
</restriction>
</simpletype>
</element>
problem here is it does not accept space i.e. <element> </element> is not acceptable.
Is there any way to force it. Please let me know.

Thanks,
figo