validation strategy

I receive messages in the form of an XML document. I am able to receive up to 44 different messages, and i therefor also have 44 different xml schemas.

When i receive a message, how do I know which schema to use to validate against?? What would you do?

If all 44 types of messages come from the same origin it would be much easier to create one schema which describes all types of messages and use this schema to validate all incoming messages.