What is an architectural style and pattern?

There are many architectural styles associated with the software that is built for computer based systems. The style describes a system category that encompasses:
- set of components.
- set of connectors enabling communication, coordination and cooperation among components.
- constraints.
- semantic models enabling a designer to understand overall properties of a system.

Architectural style is a transformation which is imposed on the design of an entire system. The intent is to establish a structure for all components of the system. When an existing architecture is re engineered, fundamental changes to the structure of the software results.
Architectural pattern imposes a transformation on the design of an architecture. Differences between pattern and style are:
- Scope of pattern is less broad.
- Pattern imposes a rule on architecture describing how software will handle some aspect of its functionality.
- Architectural patterns tend to address specific behavioral issues within context of architectural.
Patterns can be used in conjunction with an architectural style to establish the shape the overall structure of a system.