1. Three Secrets to Understanding Alloy
Plus! Two Secrets to Modeling
Roger L. Costello
August 31, 2018

2. 3 Secrets to Understanding Alloy
Everything is a set.
Sets are operated on using basic set operations: union ( + ), difference ( - ), intersection ( & ), join ( . ), etc.
Start out large (unconstrained), and then whittle down (constrain) the sets using set operations. Just like a sculptor starts out with a large piece of granite and then whittles it down into a piece of art.

3. 2 Secrets to Modeling A model abstracts away irrelevant aspects.
Example: a model of browser HTTP requests might ignore (abstract away) how network packets are structured and routed.
A model simplifies some relevant aspects.
Example: treat HTTP requests like remote procedure calls, ignore the fact that responses to requests might come out of order
Example: assume that DNS (the domain name service) is static (doesn’t change).