Software Design 2e - DIM

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chapter 589Describing a Design Solution5.1 Representing abstract ideas 5.3 Forms of notation5.2 Design viewpoints for softwareMuch of the discussion of the book has so far concentrated on examiningthe actions that are involved in the process of design, and the constraintsthat affect these. The preceding chapter began to consider theattributes possessed by the particular design medium of software; nowthis chapter starts to examine some of the ways in which these differentattributes can be described and modelled by the designer.
905.1 Representing abstract ideasDescribing a design solutionAbstraction performs an essential role in the design process, by allowing the designerto concentrate on those features of a problem or its solution that are the most importantat any particular stage in the development of the design. Therefore the designerneeds ways to represent abstract ideas about problem and design objects, and aboutthe various relationships that will exist between these. While this is a general designrequirement, and not specific to software design, the ‘invisible’ nature of software addssome problems of its own.A representation is used to provide a particular abstraction of the characteristicsof a system, and is typically needed for such purposes as:nnncapturing the designer’s ideas for a solution;explaining the designer’s ideas to others (such as customers, fellow designers,implementors, managers);checking for consistency and completeness in a solution.A representation, whatever its form, can help the designer to concentrate his or herattention upon the issue that is most important to them at any particular stage ofthe design process.* In particular, it aids the designer by providing a mechanism forreducing the problem of ‘information overload’. Indeed, as Vessey and Conger (1994)have observed: ‘human problem-solvers resort to various ways of effectively increasingthe capacity of short-term memory as well as using external memory devices and/ortechniques to support working memory’. In this context, therefore, a representationcan also be considered as providing an ‘external memory device’.Representations can also be employed across a wide range of levels of abstraction.For example, in Figure 5.1 we provide a ‘sketch’ of a building, which might be consideredto provide a good example of a ‘black box’ description, providing only a (partial)description of the external appearance of the building. Figure 5.2 provides a verydifferent representation of a specific property of the same building, in the form of adescription of a small part of the internal electrical circuitry. While this is clearly a‘white box’ description, it is still an abstraction from the final physical realization ofthe cables, switches and sockets which will be used in the circuits.Software designers similarly use a range of levels of abstraction, although theinvisible nature of software provides a particular problem in terms of how to describethe properties involved. Whereas the representation used in Figure 5.1 is fairly selfexplanatory,and even that used in Figure 5.2 has a fairly distinct link to the physicalrealization, the lack of any ‘visual’ properties for software does create a conceptual gapbetween representation and implementation. We will examine this further in Section5.3. For the moment, we should simply note that software design techniques tend tomake extensive use of various forms of box and line notations to provide visualdescriptions that are intended to represent the various properties of software.* Of course, the design process can itself be represented by the use of abstract notations, as we will see in laterchapters.
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Software Design
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Software DesignDavid Budgen
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viContentsChapter 4 Design Qualitie
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viiiContentsChapter 16 Designing wi
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xPreface to the second editiondescr
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xiiPreface to the First EditionWhy
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xivPreface to the first editionto t
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xviPublisher’s AcknowledgementsWe
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chapter 13The Nature of the Design
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Design is just as important with so
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Initialobservations7More systematic
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development. However, it should als
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From this relatively simple case st
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nnWhere possible, the panels used i
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It might well be argued that while
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system being developed. Clearly, in
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case study, the outline plan on squ
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nnnWicked problems do not have an e
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on to Pittsburgh. Airline B is the
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262.1 What is software?The software
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28nChangeability. Software suffers
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30The software design processFigure
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32The software design processthat a
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Page 146 and 147: Table 7.1The selection of black box
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Page 152 and 153: 135Black box notationsFigure 7.4A
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The ERD viewpointERDs are purely an
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141Black box notationsFigure 7.10A
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7.2.4 The StatechartLike the STD th
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145Black box notationsFigure 7.13St
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7.2.5 The Jackson Structure Diagram
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149Black box notationsFigure 7.17 A
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151Black box notationsFigure 7.19A
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153Figure 7.21The UML class notatio
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155Use case (title indicates the ac
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157cardrejectedprocesscardcard acce
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159White box notationsFigure 7.27A
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only the presence of the latter is
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In its most simple form, such a com
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NarrativeUser starts web browserUse
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If anything, pseudocode is used rat
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Many notations can be conveniently
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171Developing a diagramFigure 7.38E
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Stevens P. with Pooley R. (2000). U
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chapter 8175The Rationale for Metho
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provide a methodological analysis o
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179Figure 8.2nnSome properties of f
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ones that may be usefully supported
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183Figure 8.3The use of virtual mac
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In particular, the use of a design
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need to be recognized. Unfortunatel
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A somewhat different approach to cl
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Exercises1918.1 How would you class
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1949.1 The role of strategy in meth
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196Design processes and design stra
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212ExercisesDesign processes and de
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21410.1 Design by template and desi
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216Design patternspatterns for obje
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218Design patternsFigure 10.1A simp
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220Design patternsnnnnnnnnnnnName u
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222Design patternsFigure 10.3The pr
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224ClientRequesthandlerDesign patte
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226Design patternsout how to produc
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2281Design patternsRequirementsPatt
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230Design patternsThe patterns comm
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chapter 11233Stepwise Refinement11.
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2. The degree of modularity resulti
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compiler237lexical analysisFigure 1
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Further reading239Wirth N. (1971).
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24212.1 Black box to white box in s
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244well be to deliver a solution on
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246Incremental designpossible model
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248Incremental designnnthe roles, r
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250Incremental designFunctionalityT
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252Incremental designBusinessstudyF
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254Incremental designalthough it ma
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256ExercisesIncremental design12.1
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25813.1 Origins, development and ph
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260Structured systems analysis and
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288ExercisesStructured systems anal
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29014.1 Some background to JSPJacks
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292Jackson Structured Programming (
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chapter 15315Jackson System Develop
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317The JSD modelFigure 15.1Top-leve
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319Figure 15.3Generic form of ESD.t
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321Figure 15.6Process 1.The SSD for
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323The JSD processFigure 15.9 The J
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Entity analysis (the entity-action
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327The JSD processFigure 15.13The J
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329The JSD processFigure 15.14 The
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331The JSD processFigure 15.15 The
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333The JSD processFigure 15.16The c
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Information function step335From a
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The situation is analogous to that
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Exercises33915.1 Construct an ESD t
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34216.1 The ‘object concept’Des
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344Designing with objectsThe evolut
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346Designing with objectsFigure 16.
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348Designing with objectsFor the ob
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352 Executable units of code(subpro
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354A summary of the core concepts o
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356Designing with objectsnnnnnnnorg
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358Designing with objectsA rather l
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360Designing with objects16.2.1 Sur
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364closely at the representation pa
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366Designing with objectsAn empiric
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368Designing with objectsof a frame
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370Designing with objects16.3.2 Des
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372Designing with objectsDepartment
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376Designing with objects1. The obj
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378Designing with objectsdescribe a
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380Designing with objectsnnapproach
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382Designing with objectssequence d
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384Designing with objectsnnhow is t
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386step, it is those analysis-relat
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388Designing with objectsStep 7: De
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390Designing with objectsbehaviour,
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392indicate the degree of effort. A
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394Designing with objectsThe UP wor
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398Designing with objectsSimilarly,
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400Designing with objectswww.omg.or
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40217.1 The component conceptCompon
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404Component-based designmore than
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406Component-based designFigure 17.
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408Component-based designto address
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410Component-based designnto decomp
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412Component-based design4. Archite
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41417.3 Designing componentsCompone
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416Component-based designSourceInde
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418Component-based designwww.sei.ed
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42018.1 The case for rigourA formal
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422A formal approach to designmight
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424A formal approach to designFigur
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426A formal approach to design18.2.
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428 Table 18.1 Set operations used
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430A formal approach to designClear
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432InitResSystA formal approach to
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438A formal approach to designThis
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44018.2 Write simple Z specificatio
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44219.1 What is software now?Whithe
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444Whither software design?Figure 1
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446Whither software design?Figure 1
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448Whither software design?Another
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451BibliographyAbbott R.J. (1983).
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Buxton J. and McDermid J. (1992). H
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Guindon R. (1990). Designing the de
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Perry D.E. and Wolf A.L. (1992). Fo
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Ward P.T. and Mellor S.J. (1985). S
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462IndexCcall and return (architect
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464Indexgraphical user interface (G
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466Indexprogram design 290program i
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468WYIndexwalkthrough 81waterfall m
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