RosettaNet Large Document Validation Service

I’m trying to create a Large Document validation service for a 5C1 Pip, because Trading Networks will not use the pre-build inboundValidation if it determines that the document is large.

Has anyone created a customize large Document Validation service?
Do I need to create a schema for the common part of the Pip and one for the part that is considered large? How can I create these schemas if I don’t have a dtd?

I also need to validate the Digital Signature for the Large Document? Trading Networks will also skip the Signature validation if it’s a large document.

Any help would be appreciated.

Thanks, Fernando