software architecture patterns

It’s all too common for developers to start coding an application without a formal architecture in place. Without a clear and welldefined architecture, most developers and architects will resort to the de facto standard traditional layered architecture pattern (also called the n-tier architecture), creating implicit layers by separating source-code modules into packages. Unfortunately, what often results from this practice is a collection of unorganized source-code modules that lack clear roles, responsibilities, and relationships to one another. This is commonly referred to as the big ball of mud architecture anti-pattern. Applications lacking a formal architecture are generally tightly coupled, brittle, difficult to change, and without a clear vision or direction. As a result, it is very difficult to determine the architectural characteristics of the application without fully understanding the inner-workings of every component and module in the system. Basic questions about deployment and maintenance are hard to answer: Does the architecture scale? What are the performance characteristics of the application? How easily does the application respond to change? What are the deployment characteristics of the application? How responsive is the architecture? Architecture patterns help define the basic characteristics and behavior of an application. For example, some architecture patterns naturally lend themselves toward highly scalable applications, whereas other architecture patterns naturally lend themselves toward applications that are highly agile. Knowing the characteristics, strengths, and weaknesses of each architecture pattern is necesv sary in order to choose the one that meets your specific business needs and goals.