Access Control Service (ACS) provides a facility for abstracting your authentication code, as well as mapping disparate claims from multiple identity providers into a single token and claim structure. In addition to saving you the trouble of writing code to authenticate to many identity providers, this makes it easier to write your authorization code, as you can expect to receive a consistent set of claims from ACS.
In this chapter, we will cover ACS in depth, starting with a quick discussion of digital identities. Then we will look at ACS usage scenarios, and move into the functionality provided by ACS. Finally, we will cover some of the programming aspects.