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Software Engineering: A PractitionerSoftware Engineering: A Practitioner’’s Approach, 6/es Approach, 6/e
WVU LDCSEEWVU LDCSEE
CS 430CS 430
Fall 2004Fall 2004
copyright © 1996, 2001, 2005 R.S. Pressman & Associates, Inc.
For University Use Only May be reproduced ONLY for student use at the university level when used in conjunction with Software Engineering: A Practitioner's Approach. Any other reproduction or use is expressly prohibited.
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 2
Analysis ModelAnalysis Model --> Design Model> Design Model
Analysis Model
use-cases - text use-case diagramsactivity diagrams swim lane diagrams
data flow diagrams control-flow diagramsprocessing narratives
f l ow- o r i e nt e de l e m e nt s
c l a ss- ba se d b e ha v i or a le l e m e nt s e l e m e nt s
sc e na r i o- ba se de l e m e nt s
class diagramsanalysis packages CRcollaboration diagramsC models
state diagrams sequence diagrams D a t a / Cl a ss D e si g n
A r c h it e c t u r a l D e si g n
I n t e r f a c e D e si g n
Co m p o n e n t - L e v e l D e si g n
Design Model
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Design and QualityDesign and Quality
the design must implement all of the explicitthe design must implement all of the explicit
requirementsrequirements contained in the analysis model, and itcontained in the analysis model, and it
must accommodate all of the implicit requirementsmust accommodate all of the implicit requirements
desired by the customer.desired by the customer.
the design must be a readable, understandable guidethe design must be a readable, understandable guide forfor
those who generate code and for those who test andthose who generate code and for those who test and
subsequently support the software.subsequently support the software.
the design should provide a complete picture of thethe design should provide a complete picture of the
softwaresoftware, addressing the data, functional, and behavioral, addressing the data, functional, and behavioral
domains from an implementation perspective.domains from an implementation perspective.
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 4
Quality GuidelinesQuality Guidelines
A design should exhibit an architecture that (1) has been created using recognizableA design should exhibit an architecturethat (1) has been created using recognizable architectural styles or patterns, (2) is composed of components that exhibit goodarchitectural styles or patterns, (2) is composed of componentsthat exhibit good design characteristics and (3) can be implemented in an evolutionary fashiondesign characteristics and (3) can be implemented in an evolutionary fashion For smaller systems, design can sometimes be developed linearlyFor smaller systems, design can sometimes be developed linearly.. ^ A design should be modular; that is, the software should be logically partitioned intoA design should be modular; that is, the software should be logically partitioned into elements or subsystemselements or subsystems A design should contain distinct representations of data, architecture, interfaces, andA design should contain distinct representationsof data, architecture, interfaces, and components.components. A design should lead to data structures that are appropriate for the classes to beA design should lead to data structures that are appropriatefor the classes to be implemented and are drawn from recognizable data patterns.implemented and are drawn from recognizable data patterns. A design should lead to components that exhibit independent functionalA design should lead to components that exhibit independent functional characteristics.characteristics. A design should lead to interfaces that reduce the complexity of connections betweenA design should lead to interfaces that reduce the complexityof connections between components and with the external environment.components and with the external environment. A design should be derived using a repeatable method that is driven by informationA design should be derived using a repeatable methodthat is driven by information obtained during software requirements analysis.obtained during software requirements analysis. A design should be represented using a notation that effectively communicates itsA design should be represented using a notation that effectivelycommunicates its meaning.meaning.
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 5
Design PrinciplesDesign Principles
^ The design process should not suffer fromThe design process should not suffer from ‘‘tunnel vision.tunnel vision.’’ The design should be traceable to the analysis model.The design should be traceable to the analysis model. The design should not reinvent the wheel.The design should not reinvent the wheel. The design shouldThe design should ““minimize the intellectual distanceminimize the intellectual distance”” [DAV95] between[DAV95] between the software and the problem as it exists in the real world.the software and the problem as it exists in the real world. The design should exhibit uniformity and integration.The design should exhibit uniformity and integration. The design should be structured to accommodate change.The design should be structured to accommodate change. The design should be structured to degrade gently, even when abeThe design should be structured to degrade gently, even when aberrantrrant data, events, or operating conditions are encountered.data, events, or operating conditions are encountered. Design is not coding, coding is not design.Design is not coding, coding is not design. The design should be assessed for quality as it is being createdThe design should be assessed for quality as it is being created, not after, not after the fact.the fact. The design should be reviewed to minimize conceptual (semantic)The design should be reviewed to minimize conceptual (semantic) errors.errors. From Davis [DAV95]
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided
Fundamental Concepts Fundamental Concepts
abstractionabstraction——data, procedure, controldata, procedure, control
^ architecturearchitecture——the overall structure of the softwarethe overall structure of the software
patternspatterns——””conveys the essenceconveys the essence”” of a proven design solutionof a proven design solution
modularitymodularity——compartmentalization of data and functioncompartmentalization of data and function
hidinghiding——controlled interfacescontrolled interfaces
Functional independenceFunctional independence——singlesingle--minded function and low couplingminded function and low coupling
refinementrefinement——elaboration of detail for all abstractionselaboration of detail for all abstractions
RefactoringRefactoring——a reorganization technique that simplifies the designa reorganization technique that simplifies the design
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 10
Patterns Patterns
Design Pattern TemplateDesign Pattern Template
Pattern namePattern name ——describes the essence of the pattern in a short but expressive ndescribes the essence of the pattern in a short but expressive nameame IntentIntent ——describes the pattern and what it doesdescribes the pattern and what it does AlsoAlso--knownknown--asas ——lists any synonyms for the patternlists any synonyms for the pattern MotivationMotivation ——provides an example of the problemprovides an example of the problem ApplicabilityApplicability ——notes specific design situations in which the pattern is applicanotes specific design situations in which the pattern is applicableble StructureStructure ——describes the classes that are required to implement the patterndescribes the classes that are required to implement the pattern ParticipantsParticipants ——describes the responsibilities of the classes that are requireddescribes the responsibilities of the classes that are required toto implement the patternimplement the pattern CollaborationsCollaborations ——describes how the participants collaborate to carry out theirdescribes how the participants collaborate to carry out their responsibilitiesresponsibilities ConsequencesConsequences ——describes thedescribes the ““design forcesdesign forces”” that affect the pattern and thethat affect the pattern and the potential tradepotential trade--offs that must be considered when the pattern is implementedoffs that must be considered when the pattern is implemented Related patternsRelated patterns ——crosscross--references related design patternsreferences related design patterns
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 11
Modular Design Modular Design
easier to build, easier to change, easier to fix ...
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Modularity: TradeModularity: Trade--offsoffs
What is the "right" number of modulesWhat is the "right" number of modules
for a specific software design?for a specific software design?
optimal number optimal number of modulesof modules
cost ofcost of softwaresoftware
number of modulesnumber of modules
modulemodule integrationintegration costcost
module development costmodule development cost
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Information HidingInformation Hiding
modulemodule
controlledcontrolled
interfaceinterface
"secret""secret"
**- • algorithmalgorithm
- • data structuredata structure
- • details of external interfacedetails of external interface
- • resource allocation policyresource allocation policy**
clientsclients
a specific design decisiona specific design decision
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Why Information Hiding? Why Information Hiding?
reduces the likelihood ofreduces the likelihood of ““side effectsside effects””
limits the global impact of local designlimits the global impact of local design
decisionsdecisions
emphasizes communication throughemphasizes communication through
controlled interfacescontrolled interfaces
discourages the use of global datadiscourages the use of global data
leads to encapsulationleads to encapsulation——an attribute ofan attribute of
high quality designhigh quality design
results in higher quality softwareresults in higher quality software
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided
Stepwise Refinement Stepwise Refinement
open
walk to door;
reach for knob;
open door;
walk through;
close door.
repeat until door opens
turn knob clockwise;
if knob doesn't turn, then
take key out;
find correct key;
insert in lock;
endif
pull/push door
move out of way;
end repeat
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 19
OO Design Concepts OO Design Concepts
Design classesDesign classes
Entity classesEntity classes Boundary classesBoundary classes Controller classesController classes
InheritanceInheritance——all responsibilities of a superclass isall responsibilities of a superclass is
immediately inherited by all subclassesimmediately inherited by all subclasses
MessagesMessages——stimulate some behavior to occur in thestimulate some behavior to occur in the
receiving objectreceiving object
PolymorphismPolymorphism——a characteristic that greatly reduces thea characteristic that greatly reduces the
effort required to extend the designeffort required to extend the design
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 20
Design Classes Design Classes
Analysis classes are refined during design to becomeAnalysis classes are refined during design to become entityentity
classesclasses
Boundary classesBoundary classes are developed during design to create theare developed during design to create the
interface (e.g., interactive screen or printed reports) that theinterface (e.g., interactive screen or printed reports) that the useruser
sees and interacts with as the software is used.sees and interacts with as the software is used.
Boundary classes are designed with the responsibility of managinBoundary classes are designed with the responsibility of managingg the way entity objects are represented to users.the way entity objects are represented to users.
Controller classeController classe ss are designed to manageare designed to manage
the creation or update of entity objects;the creation or update of entity objects; the instantiation of boundary objects as they obtain informatiothe instantiation of boundary objects as they obtain information fromn from entity objects;entity objects; complex communication between sets of objects;complex communication between sets of objects; validation of data communicated between objects or between thevalidation of data communicated between objects or between the user and the application.user and the application.
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided
InheritanceInheritance
Design options:Design options:
The class can be designed and built from scratch. That is,The class can be designed and built from scratch. That is,
inheritance is not used.inheritance is not used.
The class hierarchy can be searched to determine if a classThe class hierarchy can be searched to determine if a class
higher in the hierarchy (a superclass)contains most of thehigher in the hierarchy (a superclass)contains most of the
required attributes and operations. The new class inherits fromrequired attributes and operations. The new class inherits from
the superclass and additions may then be added, as required.the superclass and additions may then be added, as required.
The class hierarchy can be restructured so that the requiredThe class hierarchy can be restructured so that the required
attributes and operations can be inherited by the new class.attributes and operations can be inherited by the new class.
Characteristics of an existing class can be overridden andCharacteristics of an existing class can be overridden and
different versions of attributes or operations are implemented fdifferent versions of attributes or operations are implemented foror
the new class.the new class.
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 22
MessagesMessages
:SenderObject
:ReceiverObject
message ()
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 23
PolymorphismPolymorphism
case ofcase of graphtypegraphtype:: ifif graphtypegraphtype == linegraphlinegraph thenthen DrawLineGraphDrawLineGraph (data);(data); ifif graphtypegraphtype == piechartpiechart thenthen DrawPieChartDrawPieChart (data);(data); ifif graphtypegraphtype = histogram then= histogram then DrawHistoDrawHisto (data);(data); ifif graphtypegraphtype == kiviatkiviat thenthen DrawKiviatDrawKiviat (data);(data); end case;end case;
All of the graphs become subclasses of a general class called grAll of the graphs become subclasses of a general class called graph.aph.
Using a concept called overloading [TAY90], each subclass defineUsing a concept called overloading [TAY90], each subclass defines ans an
operation calledoperation called^ drawdraw. An object can send a. An object can send a^ drawdraw^ message to any onemessage to any one
of the objects instantiated from any one of the subclasses. Theof the objects instantiated from any one of the subclasses. The objectobject
receiving the message will invoke its ownreceiving the message will invoke its own drawdraw operation to create theoperation to create the
appropriate graph.appropriate graph.
graphtype drawgraphtypedraw
ConventionalConventional approachapproach ……
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided
The Design ModelThe Design Model
process dimension
archit ect ure element s
int erface element s
component -level element s
deployment -level element s
low
high
class diagrams analysis packages CRC models collabor at ion diagrams
use- cases - t ext use- case diagr ams act ivit y diagr ams sw im lane diagr ams collabor at ion diagr ams (^) dat a f low diagr ams cont r ol- f low diagrams pr ocessing nar r at ives
dat a f low diagramscont r ol- f low diagr ams processing nar r at ives st at e diagr ams sequence diagr ams
st at e diagr ams sequence diagr ams
design class r ealizat ionssubsyst ems collabor at ion diagrams
design class realizat ions subsyst ems collabor at ion diagr ams
ref inement s t o:
deployment diagr ams
class diagr ams analysis packages CRC models collabor at ion diagr ams
component diagr ams design classes act ivit y diagrams sequence diagr ams r ef inement s t o: component diagr amsdesign classes act ivit y diagrams sequence diagr ams
design class r ealizat ions subsyst ems collaborat ion diagr ams component diagrams design classes act ivit y diagr ams sequence diagr ams
a na ly sis m ode l
de sign m ode l
Requirement s: const raint s int eroperabilit y t arget s and conf igurat ion
t echnical int er f ace design Navigat ion design GUI design
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Deployment Elements Deployment Elements
Figure 9. 8 UML deploy m ent diagram f or SafeHom e
Per sonal comput er
Security
homeManagement
Surveillance
communication
Cont rol Panel CPI serv er Security (^) homeownerAccess
externalAccess
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided with permission by R.S. Pressman & Associates, Inc., copyright © 1996, 2001, 2005 29
Design Patterns Design Patterns
The best designers in any field have an uncanny ability to see pThe best designers in any field have an uncanny ability to see patterns thatatterns that
characterize a problem and corresponding patterns that can be cocharacterize a problem and corresponding patterns that can be combined tombined to
create a solutioncreate a solution
A description of a design pattern may also consider a set of desA description of a design pattern may also consider a set of design forces.ign forces.
Design forcesDesign forces describe nondescribe non--functional requirements (e.g., ease of maintainability,functional requirements (e.g., ease of maintainability, portability) associated the software for which the pattern is toportability) associated the software for which the pattern is to be applied.be applied.
TheThe pattern characteristicspattern characteristics (classes, responsibilities, and collaborations)(classes, responsibilities, and collaborations)
indicate the attributes of the design that may be adjusted to enindicate the attributes of the design that may be adjusted to enable theable the
pattern to accommodate a variety of problems.pattern to accommodate a variety of problems.
These courseware materials are to be used in conjunction with Software Engineering: A Practitioner’s Approach, 6/e and are provided
FrameworksFrameworks
AA frameworkframework is not an architectural pattern, but rather ais not an architectural pattern, but rather a
skeleton with a collection ofskeleton with a collection of ““plug pointsplug points”” (also called(also called
hookshooks andand slotsslots ) that enable it to be adapted to a specific) that enable it to be adapted to a specific
problem domain.problem domain.
Gamma et al note that:Gamma et al note that:
Design patterns are more abstract than frameworks.Design patterns are more abstract than frameworks.
Design patterns are smaller architectural elements thanDesign patterns are smaller architectural elements than
frameworksframeworks
^ Design patterns are less specialized than frameworksDesign patterns are less specialized than frameworks
