One of the most important features of software architecture is the abstraction of system construction patterns；these patterns are the experiences of system designers.In the long process of developing some certain software，they have explored some regular things，summarized， and got lots of general construction patterns.In this chapter，we will bring forward some widely-used design patterns；we hope to provide plentiful reference materials for readers' system analysis and design.
It is common to use design patterns and develop methods based on patterns in many engineering fields.A well-designed universal design pattern is often the sign of a mature engineering fields techniques.The general technical nomenclature and rule have already been written into the engineering techniques handbooks and professional course materials.
At present，people's understanding about software architecture is not uniform.In the early days of software architecture，Dwayne E.perry and Alexander L.Wolf defined software architecture as：the software system family defined by software system's structure organization.Software architecture styles represent the relationships between components and components through the restriction of component application and the composition and design rule relative to components.In nowadays，the consensuses of people about software architecture styles are：a certain style or a class of styles are abstracted from the successful software system's organization structure，and can be used in different software development fields.