《Lecture 5 Design.pptx》由会员分享，可在线阅读，更多相关《Lecture 5 Design.pptx（71页珍藏版）》请在金锄头文库上搜索。
1、Design Engineering,Spring 2014,Design Engineering,It covers the set of principles, concepts, and practices that lead to the development of a high quality system or product. Goal of design engineering is to produce a model or representation that depict: Firmness program should not have any bug that i
2、nhibits its functions. Commodity suitable to its intended use. Delight - pleasurable to use. The design model provides detail about software data structures, architecture, interfaces, and components that are necessary to implement the system.,Software Design,Software design model consists of 4 desig
3、ns: Data/class Design Architectural Design Interface Design Component Design,Translating Analysis Design,Why design is so important?,It is place where quality is fostered. It provides us with representation of software that can be assessed for quality. Only way that can accurately translate a custom
4、ers requirements into a finished software product. It serves as the foundation for all the software engineering and software support activities that follow. Without design difficult to assess: Risk Test Quality,Design Process and Design Quality,Software design is an iterative process through which r
5、equirements are translated into a “blueprint” for constructing the software. As design iteration occur, subsequent refinement leads to design representation at much lower levels of abstraction.,Goal of design process,The design must implement all of the explicit requirements contained in the analysi
6、s model, and it must accommodate all of the implicit requirements desired by the customer. The design must be a readable, understandable guide for those who generate code and for those who test and subsequently support the software. The design should provide a complete picture of the software, addre
7、ssing the data, functional, and behavioral domains from an implementation perspective.,Quality Guidelines,Characteristics of good design A design should exhibit an architecture that has been created using recognizable architectural styles or patterns is composed of components that exhibit good desig
8、n characteristics can be implemented in an evolutionary fashion A design should be modular; that is, the software should be logically partitioned into elements or subsystems. A design should contain distinct representations of data, architecture, interfaces, and components. A design should lead to d
9、ata structures that are appropriate for the classes to be implemented and are drawn from recognizable data patterns.,Quality Guidelines,A design should lead to components that exhibit independent functional characteristics. A design should lead to interfaces that reduce the complexity of connections
10、 between components and with the external environment. A design should be derived using a repeatable method that is driven by information obtained during software requirements analysis. A design should be represented using a notation that effectively communicates its meaning.,Design Principles,Softw
11、are design is both a process and a model. Design process - sequence of steps that enable the designer to describe all aspects of the software to be built. Design model - created for software and provides a variety of different views of the computer based software.,Design concepts,Design concepts pro
12、vide the necessary framework for “to get the thing on right way”. Abstraction Refinement Separation of Concerns Modularity Architecture Information Hiding Functional Independence Refactoring,Abstraction,When you consider a modular solution to any problems, many levels of abstraction can be posed. At
13、 the highest level of abstraction a solution is stated in broad terms using the language of the problem environment. At lower level of abstraction a more detailed description of the solution is provided. At the lowest level of abstraction, the solution is stated in a manner that can be directly impl
14、emented.,Abstraction,As different levels of abstraction are developed, you work to create both procedural and data abstractions. Two types of abstraction: Data abstraction: collection of data that describes a data object. Procedural abstraction: a sequence of instructions that have a specific and li
15、mited function.,Data Abstraction,implemented as a data structure,E.g. Open a door. door is data object. Data abstraction for door would encompass a set of attributes describing the door. (door type, swing direction, opening mechanism, etc.),Procedural Abstraction,implemented with a knowledge of the
16、object that is associated with enter.,E.g. Open a door: open implies long sequence of procedural steps. (walk to the door, grasp knob, turn knob and pull door, etc.),Refinement,Stepwise refinement is a top-down design strategy. Refinement is actually a process of elaboration. Begin with a statement of function (or description of information) that is defined at a high level of abstraction. The statement describes function or information conceptually but provides no information about the inte
