What is software architecture (in 15 pages or less)?

Kruchten's "4+1 views of software archicture" is one of my favorite papers of all time. It shows four views of software architecture (logical/functional, process, implementation/development, and physical). The plus one is use-cases/scenarios.

Being 15 pages long, it is an incredibly efficient use of your time if you want to disentangle the different aspects of designing complex systems. And it gives you terminology for explaining what view of the system you mean, and which you have temporarily abstracted away.

Don't get hung up on the UML terminology:

• Logical is what is commonly refered to as a bubble diagram. What components are in your system and what are they responsible for?
• Process is which OS processes/threads will be running and how they communicate.
• Implementation is the files and libraries you used to build the system.
• Physical is your hardware and where you decided to map your processes.

http://en.wikipedia.org/wiki/4%2B1_Architectural_View_Model
I prefer the original paper: http://www.cs.ubc.ca/~gregor/teaching/papers/4+1view-architecture.pdf