[IEEE 1471]A system is a collection of components organized to accomplish a specific function or set of functions.The term system encompasses individual applications, systems in the traditional sense, subsystems, systems of systems, product lines, product families, whole enterprises, and other aggregations of interest.For example, most definitions indicate that an architecture is concerned with both structure and behavior, is concerned with significant decisions only, may conform to an architectural style, is influenced by its stakeholders and its environment, and embodies decisions based on rationale.All of these themes, and others, are discussed below.If you were to ask anyone to describe "architecture" to you, nine times out of ten, they'll make some reference to structure.This is quite often in relation to a building or some other civil engineering structure, such as a bridge.
[IEEE 1471]As we can see, the term "component" is used throughout these definitions.
[UML 1.5]The software architecture of a system or a collection of systems consists of all the important design decisions about the software structures and the interactions between those structures that comprise the systems.
The design decisions support a desired set of qualities that the system should support to be successful.
Structure is indeed an essential characteristic of an architecture.
The structural aspects of an architecture manifest themselves in many ways, and most definitions of architecture are deliberately vague as a result.