Software Architecture
DEFINITION Software architecture is the collection of fundamental decisions about a software product or solution designed to meet the project’s quality attributes (the architectural requirements). The architecture includes the main components, their main attributes, and their collaborations (their interactions and behavior) to meet the quality attributes. Architecture can, and usually should, be expressed in several levels of abstraction, where the number of levels depends on the project’s size and complexity.
● Architecture occurs early. It should represent the set of earliest design decisions that are both hardest to change and most critical to get right.
● Architecture is an attribute of every system. Whether or not its design was intentional, every system has an architecture.
● Architecture breaks a system into components and sets boundaries. It doesn’t need to describe all the components, but the architecture usually deals with the major components of the solution and their interfaces.
● Architecture is about relationships and component interactions. We’re interested in the behaviors of the individual components as they can be discerned from other components interacting with them. The architecture doesn’t have to describe the complete characteristics of the components; it mainly deals with
their interfaces and other interactions.
● Architecture explains the rationale behind the choices. It’s important to understand the reasoning as well as the implications of the decisions made in the architecture because their impact on the project is large. Also, it can be beneficial to understand what alternatives were weighed and abandoned. This may be important for future reference, if and when things need to be reconsidered, and for anyone new to the project who needs to understand the situation.
● There isn’t a single structure that is the architecture. We need to look at the architecture from different directions or viewpoints to fully understand it. One diagram, or even a handful, isn’t enough to be considered an architecture.
SOA
DEFINITION Service-oriented architecture (SOA) is an architectural style for building systems based on interactions of loosely coupled, coarse-grained, and autonomous components called services. Each service exposes processes and behavior through contracts, which are composed of messages at discoverable
addresses called endpoints. A service’s behavior is governed by policies that are external to the service itself. The contracts and messages are used by external components called service consumers.
SOA patterns and their relationships
