软件开发设计外文翻译文献本科毕业论文

1、外文资料原文Software Development Concepts and DesignMethodologiesDuring the 1960s,main framesand higher levelprogram mingIan guageswere applied to many problemsin cludi nghuma n resourcesystems, reservati on systems, and manu facturi ng systems. Computers and software were see n as the cure all for many b

2、us in ess issues weresometimes applied bli ndly.Systems sometimes failedtosolvethe14problem for which they were desig ned for many reas ons in cludi ng:?ln ability to sufficie ntly un dersta nd complex problems?No tsufficie ntlytaking intoacco untend -userneeds,theorga ni zati onal en vir onment, an

3、d performa nee tradeoffs?In abilityto accuratelyestimatedevelopme nttimeandoperati onal costs?Lack offrameworkforcon siste ntand regularcustomercom muni cati onsAt this time,the con ceptofstructuredprogrammi ng,top -downdesig n, stepwiserefin eme ntandmodularityemerged.Structuredprogram mingisstillt

4、hemostdominantapproach tosoftwareengineering and is still evolving. These failures led to the conceptof software engineeringbased upon the ideathat an engineering -likediscipli ne could be applied to software desig n and developme nt.Software desig n is a process where the software desig ner applies

5、techniquesand principlesto produce a conceptual model that d escribesand defines a solution to a problem. In the beginning, this design process has not bee n well structured and the model does not always accurately represe nt the problem of software developme nt. However,design methodologies havebee

6、n evolvingto acc ommodatechangesintech no logy coupled with our in creased un dersta nding of developme nt processes.Whereas early desig n methods addressed specific aspects of thedevelopme nt process, curre nt methods attempt to address the en tirescope of software developme n t. Softwaredesig nmet

7、hods areofte nclassified in reference to the period in which they were introduced and the problems at that time. Driven by coding and testing problems, tools and methods were developed. Early methods focused on modularity and top-down development, and informationhidingthroughabstraction.This led to

8、the developme nt of structuredIan guages,structuredan alysis, and data flow an alysis.In the last decade or so, the expe nse in volved in automati on hasshifted from hardware to people. Therefore, the software engin eeri ngcom munity has bee n focused on object orie nted (O-O) desig n and thecon cep

9、t of re -usable code in order to reduce thehuma n cost comp onent.In efficie ntdesig ns and developme ntmethodologies have bee n addressedwith Computer Aided SoftwareEngin eeri ng(CASE) tools, and fourthgen erati on desig n Ian guages. This has bee n done in an attempt replace the traditi onal water

10、fall life cycle process model un der which most exist ing software has bee n developed.一、 Software Desig n Fun dame ntalsSoftware desig n methods all aim to provide the software desig nerwith a systemblueprint.This blueprint usually has three aspects:data,architectural, and procedural.?Data desig n

11、refers to the datas orga ni zati on, relatio nships,access and processing methods.?Architectural desig n defi nes the comp onents of the system andtheir relati on ships.?Procedural desig n builds on the data and architectural desig nphases to describe the process ing details of the system.thodologie

12、s, their basicEven though there are nu merous desig n mecon cepts are very similar-All software desig n methods partiti on the high level la nguage developed in the late 60s that in troduced object classes as a method to encapsulate data. Later, in the 1970s, Smalltalkproblem and softwareinto smalle

13、r pieces in order to reducecomplexity.They all strive toide ntifydata structuresand functions.and providemeasureme nts for software quality. Some of the com mon prin ciples insoftware desig n in clude: stepwise refin eme nt, software architecture,program structure, data structure, software procedure

14、s,m odu l ar i t y,abst r act i on, and inf or mat i on hi d ing.Moder n Desi gn Met hodol ogi esConventional s of t wa r e d evel opme nt p r act i ces cangen e r a l l y b ema pp e d onto t he traditi onal life-cycle phases ofanal y si s ,f u net i on a Is peci f i cat i on, desi g n, impleme ntat

15、i on, test ing, andmaintenan ce. Thi s t h ough t pr oces s i s in ad eq u at e for t oday sc o mpl ex i nf or mat i on s yst ems. As the dema nd for software is grow ingmuch faster tha n the nu mber of developers, adheri ng to conven ti onaltechniques such as the waterfall method requires too much

16、time, too manypeople, and is difficultto man age. Hen ce,many new softwaredevelopme nttech no logies havearise n. N ewl y d evel oped p r act i ces a nd mode l s d o notat t empt t o separ at e phases of sof t war e development, such asspecificati on and impleme ntati on, but in stead focus on the c

17、on cept ofprogram tran sformatio n through stepwise refin eme nt and iteratio n.1、Obj ect - Or i ent ed Technol ogyObject-Orie nted(O-O) softwaredesig ntech no logyis fun dame ntallydiffere nt from thetraditi onal methods described above. Withtraditi onal methods, each module is recog ni zeda major

18、step in theoverall process and the process goes from one step to the n ext. On the other hand, O-O desig n is structured around a model of objects and the functions they perform.O-O programming can be traced to the simulation Ianguage SIMULA, awas introduced asa complete grap gh design and codingas

19、detail is addedto the desig n. This provides a com mon Ian guage throughout each stagein developme nt.O-O is best applied with specificallydesig ned0-0developme nttools, butit is importantto remember thatas a methodologyis it notspecificto any program mingIan guage.Many differe ntprogram mingIan gua

20、gescan be used to impleme nt0-0tech no logyanddesig n methodologies.In stead of procedures and functions pass ing data back and forth, inobject orie nted desig n, the system is viewed as a collect ion of objects with messages passed from object to object. Each object has its own setof associated ope

21、rati ons. Object-orie nted desig n is based on the ideaof information hiding and modularization of both data and processing.It is best used when n either data structure nor process ing operati onsare well defi ned aheadof time.This isquite usefulin todays bus in essenvironmentwhererequireme ntsareal

22、ways cha ngingand notvery welldefi ned.Thus, ithas becomequitepopular!Theconceptof objectsperform ing services is a n atural way of thi nki ngfor both developers andcustomers. This facilitatesun dersta ndingthe problem doma in and a moren atural desig n. In additi on, there are many ben efits of obj

23、ect-orie nteddevelopme nt. These in clude:? In herita nee capitalizeson the com mon alty of attributesandservices allow ing code and objects to be re-used.Informationhidi ng makes systems more stablebylocaliz ingcha nges to objects andthereby maki ng them reusable.Theobject-orienteddevelopme ntproce

24、ss iscon siste ntfroman alysis, through desig n,to codi ng.More in formatio n on Object Orien ted Programmi ng prin ciples can befound in Chapter4-Orga ni zati onof Programmi ngLanguagesandProgrammi ng Con cepts.2、 P r ot ot y pi ngPrototyp ingwas inven ted because end users participati ngin thedeve

25、lopme nt phase found it difficultto un dersta ndrequireme ntspecificati ons and con ceptual models. However, whe n it first bega n being used in the 1980s, most conven ti onallife cycle developerscon sidered it expe nsive and time consuming.Since t hat time, users and de vel oper s have used prot ot

26、 ypes s u cces sf u l l y as acom muni cati onstool todem on stratesystemrequireme nts. After several prototype iterati ons,developers have abetter un dersta nding of user requireme nts and users have a better idea of how the system will eve ntually work, look, andl.The nu mb er of t i mes t he p r

27、ot ot y pe i s in cr e me nt al I y ref i ned d e pe nds o n h ow w el l t he u ser r eq u i r e me nts and u n der st ood. I t also d e pe nds on t he users n eed t o a dd r equ i r e me nts o r c ha nge previously stated r eq ui r e me nts. Af t e r es t abl i s h ing an overall architecture and f

28、 r a me wo r k, t he system i s d e ve l oped and del i ver ed i n i n c r eme nts.Us er s may e x pe r i ment w i t h and use deli ve r ed i n c r e me nts whi l e o t hers are being devel oped. For in s t a nee, t he first p r ot o t y pe may bedel i ve r ed t h at i mpl e me nts a c er t a i n sc

29、ree n w i t h onl y s o me a c t i veme n u i t e ms.Whi l e users are exper imenti ng wi t h t hi s scree n and menui t ems , ot herscree ns and menu i t emsare con cur r e ntl y b e i ng d e ve l opedwhi ch l at erwil l be combi ned wi th t he existing prototypeas ie v ol ves.On ce t heuser i s sa

30、t isf i ed t hathe prototypemeetr e q ui r e me nts,t he pr o t o t y pes t ran s f o r mednt o t he syst em.Thieffort depends on sever alf act or s.may in cl ude ad dingfun ct i on a l i t y t hat wa s ntini t i al Irecogni zed asr eq u i red,r eplaci ng i nef f i ci ent p artso f t he pr otot y pe

31、 t o m eet pe r f o r ma neecr i t er i a, o r adapt ing t he prot ot y pef i t t he users har d war een vi r onment.Prototyp ing can beg in very early, af t er s o me p r el i min ary requireme nts an al y s i s has determ ined t he bas i c fun ct i on al i t y, scope, and en vi r o nmen toft he p

32、r oposed s of t war e. Con t r a r y t o t he t r adi t i onal wa t er f a l l met hod, in t he p r ot o t yp ing, fun ct i onal s peci f i cat i ons are not f i xed. Rat her, users ar e en couraged t o mo d i f y t heir r eq u i r eme nts a s t hey t hemselves b eg in t o un d er s t a nd them bet

33、t er. Thi s i s because users of t e n don t r eal l y kn owwhat t hey wantun t i l t hey s ee i ton t he s cr ee n. T he p r ot ot y p ing p r oces s o f d e mo nstrati on, r evi ew, and r ef inemen t g et s t he user mor e i n vol ved i n t he deve l op me nt p r ocess , gi vi ng t hem a sense of

34、own e r s hi p d u r i ng t he process and at final system deli very. Howe ve r, d ue t o t he min ds et o f prototype, users of t e n fin d i t di f f i c ul t t o ve r i f y t hat t he p r ot ot y pe s at i sf i es t hei r r eq u i r e me nts. T her ef ore, g ui de l ines must be est abl i s hed t

35、 o determ i ne whe n t o st op i t er at ing and t he p r ot ot y pe t o final pr od u ct.外文资料译文软件开发概念和设计方法在20世纪60年代，大型机和高级程序语言被用来解决包括人力资源系 统、专有系统和制造系统等许多问题。计算机和软件被视为解决所有商业问 题的万能药，有时候甚至被盲目的应用。因为很多设计上的原因，这些系统 并不是万能的。主要因素如下：1 不能完全理解复杂的问题2 没有充分满足终端用户的需求，组织环境和性能折中3 没有准确估计开发时间和运行成本4 缺乏一致，规范的客户通讯框架这个时候，结构

36、化的编程，自上而下设计的概念出现了。对软件工程来 说，结构化编程至今仍是最重要的方法且不断发展。“软件工程”概念的出现 则是基于这样的构想：一个类似工程学的学科可以应用于软件的设计和开发。软件设计是一种方法，软件设计人员可以籍此应用技术和规则生成一种 描述并定义问题解决方法的模型。最初，设计方法一直未能构建好，而且模型 也不能准确地描述软件开发的问题。然而，随着我们对开发过程的深入理解， 设计方法已经不断适应技术的变化了。生命周期过程的模型下开发的，但人们开始尝试寻找这种模型的替代品。 一、 软件设计基础软件设计方法最终的目标就是向软件设计者提供一张系统蓝图。它通常有 三个方面：数据，构架和过

37、程。 数据设计指的是数据的组织、关系、访问和处理方法。构架设计定义系统组件和它们之间的关系。过程设计建立在数据和构架设计阶段之上描述系统的处理细节。尽管设计方法众多，但它们的基本概念非常相似。为了减少复杂度，几乎 所有软件设计方法都把问题和软件分割成较小的部分用于标识数据结构、功能 以及度量软件品质。软件设计包括以下这些普遍原则：逐步求精、软件构架、 程序结构、数据结构、软件过程、模块化、抽象和信息隐藏。二、 现代设计方法常规的软件开发实践通常能被映射到传统的生命阶段上，包括分析、功能 说明、设计、实现、测试和维护。然而对软件需求的增长比软件开发者数量增 长要快，遵守常规的技术你瀑布模型）耗时

38、太长，过多人员的参与也带来了 管理上的困难，显然常规的思考过程对于今天的复杂信息系统是不够的。因 此，产生了许多新的软件开发技术。最新发展出的实践和模型井不试图把软 件开发分割成多个阶段（如说明和实现），而是注重于通过逐步求精和迭代把 概念转换成程序。1、面向对象的技术面向对象的软件设计技术从根本上有别于传统的设计方法。传统方法中， 每个模块被当作全局过程的一个主要步骤，一步一步地往下走；而面向对象 的设计围绕着对象模型和对象所执行的功能进行结构化。面向对象的编程可以追溯到仿真语言SIMULA。SIMULA是一种20世纪60 年代后期的高级语言，引入了“对象类”作为封装数据的方法。到了 20世

39、纪 70年代，Smalltalk 被作为一种完全的图形用户界面（GUI ）面向对象的编程 环境被引入。甚至在30年以后，Smalltalk 仍然是度量其他所有面向对象语 言的标准。由于面向对象的概念日趋成熟，最近十年这种软件开发方法已经 流行起来。同时，软件业注意的焦点己经从编码和结构化过程转移到通过设 计和柔韧性来节省劳动力成本和时间。柔韧性变得十分关键，因为系统随着 需求的变化而快速改变：变得更大，更复杂和更不稳定。在面向对象中，分析和设计没有真正分开。在分析期间，系统对象及其 特性和关系一起被确定。这些对象可以护，这样就给整个开发过程中的所有 阶段提供了一种公用的语言。采用面向对象方法最

40、好是使用专门设计的面向 对象的开发工具，但是请一定记住它是一种方法而不是特指任何编程语言。 许多不同的编程语言都可以用来实现面向对象技术和设计方法。和过程、功能往返传递数据的方式不同，在面向对象的设计中，系统被 看成一个由很多互相传递消息的对象组成的集合，每个对象都有它自己关联 操作的集合。面向对象的设计基本构想是把数据和过程进行信息隐藏和模块 化，它最适用于数据结构或者过程操作没有被提前的定义好的情况。这对于 今天的商业环境中相当有用，毕竟需求总是不断改变而不能很好的定义。这 也是面向对象的设计现在相当流行的重要原因。对象执行服务的概念是一种 开发者和客户都很自然的思考方法，这有利于理解问题的范围，也是一种更 加自然的设计。此外，面向对象的开发还有许多优点。通过属性和服务的结合使用，继承可以重用代码和对象。信息隐藏通过局限对象的变化使系统更加稳定，从而使对象可以重用面向对象的开发过程从分析、设计到编码都是一致的。2、原型法原型法的出现是因为参于开发阶段的终端用户觉得很难理解需求说明和 概念模型。而当原型法在20世纪80年代第一次被使用时，大部分常规的生 命周期开发者认为它费时费力。但从那时开始，用户和开发者已经能成功地 应用原型作为通讯工具来演示系统的需求。原型多次迭代后，开发者对用户 的需求有了更好的理解，用