Mark W. (Centreville, VA, USA) Maier & Eberhardt (University of Southern California, Palos Verdes, USA) Rechtin 
The Art of Systems Architecting [EPUB ebook] 

If engineering is the art and science of technical problem solving, systems architecting happens when you don”t yet know what the problem is. The third edition of a highly respected bestseller, The Art of Systems Architecting provides in-depth coverage of the least understood part of systems design: moving from a vague concept and limited resources