If you look for a well specified framework for ambient computing, I recommend you search for "Edge Computing". There is a solid "ETSI ISG MEC " framework you could use.
The answer may vary depending on framework / application you want to develop. Let's say you want to develop smart health ambient application. Suppose you have to observe the patients and help them in non-invasive way. This application may use different computing domains like sensor networks, communication technologies, middle-ware, artificial intelligence,
intelligent learning, computer vision etc. In each such main domain, we may have different sub-domains like security, privacy, context awareness, behavior monitoring and so on.