How to disallow empty string elements using XML Schema?

[=?ISO-8859-1?Q?Jan-Erik_=D6hman?=]

Hi.
I want to do something like
<root>
<n>Some text only</n>
</root>

I wan't to define a schema that disallows the following xml-files:
<root>
<n/>
</root>
and
<root>
<n></n>
</root>

where the node 'n' is specified in the schema as xsd:string.

Is this possible? I haven't figured out how to do this.

Anyone know how to do this?

Thanks in advance, Jan-Erik