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翻译日期： 2017.02.14
外文资料原文
Software Development Concepts and Design
Methodologies
During the 1960s, ma inframes and higher level programming languages were applied to man y problems including human resource s yste ms,reservation s yste ms, and manufacturing s yste ms. Computers and software were seen as the cure all for man y bu siness issues were some times applied blindly. S yste ms sometimes failed to solve the problem for which the y were designed for man y reasons including:
•Inability to sufficiently understand complex problems
•Not sufficiently taking into account end-u ser needs, the organizational environ ment, and performance tradeoffs
•Inability to accurately estimate development time and operational costs •Lack of framework for consistent and regular customer communications At this time, the concept of structured programming, top-down design, stepwise refinement，and modularity e merged. Structured programming is still the most dominant approach to software engineering and is still evo lving. These failures led to the concept of "software engineering" based upon the idea that an engineering-like discipl ine could be applied to software design and develop ment.
Software design is a process where the software designer applies techniques and principles to produce a conceptual model that de scribes and defines a solution to a problem. In the beginning, this des ign process has not been well structured and the model does not alwa ys accurately represent the problem of software development. However,design methodologies have been evolving to accommo date changes in technolog y coupled with our increased understanding of development processes.
Whereas early desig n methods addressed specific aspects of the
develop ment process, current methods atte mpt to address the entire scope of software development. Software design methods are often classified in reference to the peri od in which the y were introduced and the problems at that time. Driven b y coding and testing problems, tools and methods were developed. Early methods focused on modularity a nd top-down development, and information hiding through abstraction. This led to t he development of structured languages, structured analysis, and data flow analysis.
In the last decade or so, the expense involved in automation has shifted from hardware to people. Therefore, the software engineering community has been focused on object oriented (O-O) design and the concept of re-usable code in order to reduce the human cost component. Inefficient designs and develop ment methodologies have been addressed with Computer Aided Software Engineering (CASE) tools, and fourth generation design l anguages. This has been done in an attempt replace the traditional waterf all life c ycle process model under which most existing software has been developed.
一、Software Design Fundamentals
Software design meth ods all aim to provide the software designer wi th a s yste m blueprint. This blueprint usually has three aspects: data, architectural, and procedural.
•Data design refers to the data's organization, relationships, access and processing methods.
•Architectural design defines the components of the sys tem a nd their relationships.
•Procedural design builds on the data and architectural design phases to describe the processing details of the s yste m.
Even though there are numerous design methodologies, their basic concepts are ver y similar-All software design methods partition the problem and software into smaller pieces in order to reduce complexity. They all strive to identif y data structures and functions, and provide measur ements for software quality. Some of the common principles in software design include: stepwise refinement, s oftware architecture, program structure, data structure,
