System architecture is the conceptual model that defines the behaviour, structure, and views of a system. Systems are a class of software that provides foundational services and automation. Architecture can be planned upfront or emerge over time. It includes elements such as services, layers, components, relationships, technologies, standards, principles, conventions, and constraints. 

Architecture can be evaluated based on business objectives in areas such as cost, functionality, reliability, maintainability and operability. In other words, a poor architecture can be costly, unreliable and difficult to maintain, operate, change and extend.