I am a newbie in this PPM and trying to understand the system.
Could you please tell me whats the role of webservices in PPM (from Demand Management perspecctive)?
I could see documentation on whats development process is then WSDL and SOAP usages, but not sure why should one use them here in PPM. As I understand, its a client server model where in client will send request and server will respond back with a response.
Web services is just a way for other applications/systems to interact with PPM. It's an API that developers can use so they can, say, program another app to be able to create a request in PPM or look up the status of a particular request.
If you don't have a need for other systems to programatically interface with PPM, then it's not required.