Putting SQL to Work(Chapter 9 of Hello, Android)

　　Android programs can communicate with each other in two ways:

　　• Inter-Process Communication (IPC): One process declares an arbitrary API using the Android Interface Definition Language (AIDL) and the IBinder interface. Parameters are marshaled safely and efficiently between processes when the API is called. This advanced technique is used for remote procedure calls to a background Service thread.

　　• ContentProvider: Processes register themselves to the system as providers of certain kinds of data. When that information is requested, they are called by Android through a fixed API to query or modify the content in whatever way they see fit.