System Design Document for SaaS

We’re in the process for validating an application service providers web application for training, I’m struggling on what to put in the SDS. We don’t know the design of the vendors application and they are less than cooperative on providing something. We have a configuration spec. Does anyone have any suggestions on how to overcome this?

Did you not give the vendor a URS document and ask them to map out how each requirement is satisfied in the FS and SDS.

On what basis did you purchase the application, how was the decision made to go with this system if the URS was not satisfied!

Its a common problem in our industry I’m afraid, individuals making decisions on applications without good knowledge of what they require.