All,
I'm a developer on android platform. we want to develop a new app. When we write a makefile for the app, we notice, for variable LOCAL_MODULE_TAGS, we can define it as user, eng or something else.

Could someone please share some basic information on what the differency between 'user' and 'eng' and some others? Which one we should use for our apps?

another question is: how to make sure the app can be build and included into system.img? Which makefile we should modify? is there any detailed description on android build system?

Thanks very much