External Definition: Name contains invalid characters: -

When I try to import an XSD file as external definition in PI 7.1 I get the error:

Name contains invalid characters: -

Only a(A)-z(Z), 0-9, and "_" are permitted

The XSD file describes a standard XML format, which is required for the project. I get the same error when I try to manually define a data type with a - in the name. Is there a way to get PI running with data types with a - in the name or have I made a mistake when I was importing the definition? As far as I know "-" is quite common in xml tags (e.g. http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd)

Thanks and regards,

Tarik