Proposal for API "service" usage

Hi all,

please find attached a proposal for an addition to the API document to
demonstrate the "service" usage. The idea is to add to each section a "Usage
as a service" part, with information about request / response patterns. It
would be great if you could have a short look at this during the f2f
meeting. If you agree with that kind of addition, I could take the API
document and make them for all property sections.

Thanks,

Felix