OpenService API

I would like to start a conversation about the idea of having what can be called „OpenService API“ that enables to develop services that can be used anywhere that supports that API (something similar to the OpenID and OpenSocial concepts but in a service provisioning/integration context). The „OpenService API“ should not only be based on HTML and JavaScript as it is the case with Google Gadgets API for instance; it can also use SOA technologies (e.g. REST, SOAP etc.).
In my opinion, this can be very useful for the extensibility of Personal Learning Environments (PLE). I can imagine to design and develop a PLE Framework (PLEF) that supports the “OpenService API” such that services based on that API can easily be plugged into the framework.

What do you think? Do we really need this? What are the requirements of such an API?

I would also be very thankful if you can point me to existing ideas in this direction.