webservice versioning in 7.1.3???

Hi,
We have the below requirement:
Release 1: Develop a webservice with one operation (Add) in it.
This operation has two input parameters which are mandatory.
Release 2: The Add operation now should be able to add three numbers that are given in the input. So we need to add one new input field which is also mandatory.
No seperate WSDL URL or Add operation should be created. We can only update the existing WSDL.
Post release 2, the webservice clients which send only two input values fail.
What are the approaches to implement the above requirements without breaking the existing clients?
Someone suggested to version the targetnamespace in the WSDL. I din’t really get what they mean. Not sure how that can be implemented in wM.
Please suggest.
We need this to be implemented in 7.1.3.
We dont have Centrasite as of now.

Regards,
Ravi

If i understand you correctly, R1 & R2 are logically conflicting. So, after R2, on server side you have only one service that require 3 parameters. No matter how you twick your WSDL, it won’t work with the old client.
You’d better create a new service + new WSDL for R2.

“Post release 2, the webservice clients which send only two input values fail.
What are the approaches to implement the above requirements without breaking the existing clients?”

These are contradictary behaviors. If you’re trying to support both 2- and 3- parameter add operations, you’ll need to have separate add operations.

Thanks tongwang and Rob