SAM can also be used for stateful API/Microservice orchestrations [2]
If you want a slightly more formal introduction to SAM and its relationship to TLA+ (again, based on my own interpretation) I gave this lecture last month [3].
[2] http://www.ebpml.org/blog15/2015/06/designing-a-reliable-api...
[3] http://cloudsentinel.com/sam-state-machines-and-computation....