Vipul Pathak

Casually speaking, Software architecture is the careful partitioning or subdivision of a system as whole, into sub-parts with specific relationship between these sub-parts. This partitioning is what allows different people (or group(s) of people) to work together cooperatively to solve a much bigger problem, then any of them could solve by individually dealing with it. Each person (or team of persons) creates a software part (you may want to call it a component, module or a sub-system) that interacts with other person’s (or team’s) software part. This interaction happens through carefully crafted interfaces that exposes minimum but most stable information necessary for interaction.

The larger and complex the system is, the more critical is this subdivision. A system is almost always, unavoidably can be divided into parts in more than one way. Each way of division, results in creation of architectural structure. Each way of dividing the system into parts, relationships between them and the way they interact (interface), is a result of careful design to satisfy the driving quality attribute (security, performance, changeability etc.) and business goal behind them. So a system may be sub-divided into parts in different ways, if the driving quality attribute or business goal is different.

Finally, a formal definition of software architecture from IEEE –

“The fundamental organization of a system embodied in its components, their relationships to each other, and to the environment, and the principles guiding its design and evolution.”

Why architecture is important?

Software architecture is a set of design decisions which are hard to revert later and if made incorrectly, may cause the project to cancel or be unsuccessfully. Since these architectural design decisions are the ones that permits a system to meet its quality attributes and behavioral requirements, if these decisions go wrong, the system cannot achieve the desired quality or behavior. The quality attributes are usually parts of requirements (non-functional requirements) and failing to fulfill these requirements automatically invalidate the solution.