Systems architecture

A system architecture is the conceptual model that defines the structure, behavior, and more views of a system. An architecture description is a formal description and representation of a system, organized in a way that supports reasoning about the structures and behaviors of the system.
A system architecture can consist of system components and the sub-systems developed, that will work together to implement the overall system. There have been efforts to formalize languages to describe system architecture, collectively these are called architecture description languages (ADLs).
Overview.
Various organizations can define systems architecture in different ways, including:
One can think of system architecture as a set of representations of an existing (or future) system. These representations initially describe a general, high-level functional organization, and are progressively refined to more detailed and concrete descriptions.
System architecture conveys the informational content of the elements consisting of a system, the relationships among those elements, and the rules governing those relationships. The architectural components and set of relationships between these components that an architecture description may consist of hardware, software, documentation, facilities, manual procedures, or roles played by organizations or people.
A system architecture primarily concentrates on the internal interfaces among the system's components or subsystems, and on the interface(s) between the system and its external environment, especially the user. (In the specific case of computer systems, this latter, special, interface is known as the computer human interface, "AKA" human computer interface, or HCI; formerly called the man-machine interface.)
One can contrast a system architecture with system architecture engineering (SAE) - the method and discipline for effectively implementing the architecture of a system:
History.
Systems architecture depends heavily on practices and techniques which were developed over thousands of years in many other fields, perhaps the most important being civil architecture.
Types.
Several types of systems architectures (underlain by the same fundamental principles) have been identified as follows: