Regardless of the development process that you use, a description of the software architecture can be essential for any project, big or small. If software architecture is about the structure of a system and is the vehicle for satisfying the requirements, then the software architecture document is a written description of this. My simplified view of the content included in a software architecture document is :
During our tutorial last week at QCon, we asked attendees to define the software architecture for a small software system and provided a handout containing some guidelines. Since this may prove useful for other people, we're making Software Architecture Document Guidelines v0.1 available for download.
It's worth remembering that the software architecture doesn't have to be a huge weighty tome and it doesn't even need to be a traditional Word document. What's important is that you capture the important architectural decisions and principles. This set of guidelines includes suggestions for what you might want to include. Just as a final note, this set of guidelines is a work in progress and we'll be iterating it over the coming months. Any feedback is welcome.
Simon is an independent software development consultant specialising in software architecture; specifically technical leadership, communication and lightweight, pragmatic approaches to software architecture. He is the author of two books about software architecture; Software Architecture for Developers (a developer-friendly guide to software architecture, technical leadership and the balance with agility) and The Art of Visualising Software Architecture (a guide to communicating software architecture with sketches, diagrams and the C4 model). Simon lives in Jersey (the largest of the Channel Islands) and regularly speaks to audiences around the world. You can find Simon on Twitter at @simonbrown.