Advanced topics in software engineeringAdvanced topics in software engineering CSC532 CSC532

Term Paper Term Paper

Design PatternsDesign Patterns

Harpreet Singh

Submitted By:-

IntroductionIntroduction

What are Design patterns ?What are Design patterns ?

A standard solution to problems in object oriented A standard solution to problems in object oriented

software developmentsoftware development

A well formed language to represent the software designA well formed language to represent the software design

Ready made and Proven solution for some recurring Ready made and Proven solution for some recurring problemsproblems

How did the need for Design Patterns raisedHow did the need for Design Patterns raised

Look at Problem:-Look at Problem:-

Hundred and thousands of Software Projects made each yearHundred and thousands of Software Projects made each year Not all of the Software Development techniques are differentNot all of the Software Development techniques are different Developers don’t invent a new design all the TimeDevelopers don’t invent a new design all the Time A procedure should be present to reuse the existing design work in A procedure should be present to reuse the existing design work in

order to save time and Moneyorder to save time and Money

Solution :-Solution :- DESIGN PATTERNSDESIGN PATTERNS

How are Design Patterns the solutionHow are Design Patterns the solution

Provide ready to use and proven DesignProvide ready to use and proven Design

Represent the expertise of whole community so reduce Represent the expertise of whole community so reduce the chances of problemsthe chances of problems

Help novice developers to learn the process easilyHelp novice developers to learn the process easily

Better quality software is developedBetter quality software is developed

History of Design PatternsHistory of Design Patterns

Term coined byTerm coined by Christopher Alexander Christopher Alexander

He was an Architect and a BuilderHe was an Architect and a Builder

Made the Design Patterns for Buildings Made the Design Patterns for Buildings

Not of much use as only few used it.Not of much use as only few used it.

How were Design patterns used in SoftwareHow were Design patterns used in Software

WWard Cunningham and Kent Back used some of the ideas of ard Cunningham and Kent Back used some of the ideas of

Alexender for User Interface DesignAlexender for User Interface Design

Most significant work done byMost significant work done by :- :-

Erich Gamma, Richard Helm John Vlissides Erich Gamma, Richard Helm John Vlissides

and Ralph Johnson and Ralph Johnson

Wrote the book :-Wrote the book :-

Design Patterns: Elements of Reusable Object-Oriented SoftDesign Patterns: Elements of Reusable Object-Oriented Softwareware

popularly called popularly called “ Gang Of Four ”“ Gang Of Four ”

Classification ofClassification of Design PatternsDesign Patterns

Design Pattern Classification

Purpose Scope

Creational Structural Behavioral

Class Object

PurposePurpose

What the pattern will do or has done in the pastWhat the pattern will do or has done in the past

Creational StructuralCreational Structural BehavioralBehavioral

Scope Scope Where the pattern would be appliedWhere the pattern would be applied

ClassClass ObjectsObjects

Creational Creational

Deals with object creation mechanismDeals with object creation mechanism

Structural Structural

Identifies ways to realize relationships between the Identifies ways to realize relationships between the entities that are used in the software developmententities that are used in the software development

BehavioralBehavioral

identify common communication patterns between the identify common communication patterns between the objectsobjects

ClassClass

Patterns mainly deal with relationships between classes and Patterns mainly deal with relationships between classes and their subclasses. their subclasses.

Static as they are established through inheritanceStatic as they are established through inheritance..

ObjectObject

Patterns in this category deal with object relationships . Patterns in this category deal with object relationships .

Relationships are dynamic in nature and can be changed at Relationships are dynamic in nature and can be changed at

runtimeruntime

Documenting the Design PatternsDocumenting the Design Patterns

One of the toughest taskOne of the toughest task

Should provide fact and complete information Should provide fact and complete information about the problem and its Domainabout the problem and its Domain

Should help users to investigate existing system Should help users to investigate existing system and customize it to fit users needs and customize it to fit users needs

Characteristics of DocumentationCharacteristics of Documentation

Pattern name and classificationPattern name and classification

IntentIntent MotivationMotivation Applicability Applicability StructureStructure ParticipantsParticipants Implementation Implementation Known usKnown usee

Related patternsRelated patterns

Critique of Design PatternsCritique of Design Patterns

Don’t always provide the relevant solutionDon’t always provide the relevant solution

Experiments performed on OBSERVER, COMPOSITE, Experiments performed on OBSERVER, COMPOSITE,

VISITOR are examplesVISITOR are examples

Need only arises due to insufficient AbstractionNeed only arises due to insufficient Abstraction

Complicate the problems even more in some situationsComplicate the problems even more in some situations

ConclusionConclusion

Design patterns are very useful as they provide ready Design patterns are very useful as they provide ready to use and proven solutions that speed up to use and proven solutions that speed up development and improve software qualitydevelopment and improve software quality

They do have limitations and negative points but their They do have limitations and negative points but their benefits overpower the limitationsbenefits overpower the limitations

Unless there is clear need to use simpler solutions the Unless there is clear need to use simpler solutions the design patterns should be used as they provide more design patterns should be used as they provide more flexibilityflexibility

ReferencesReferences 1.1. Formal specification of design patterns: a comparisonFormal specification of design patterns: a comparison

Taibi, T.; Ling, D.N.C.;Taibi, T.; Ling, D.N.C.;

2.2. Evolutionary patterns of design and design patternsEvolutionary patterns of design and design patternsAoyama, M.;Aoyama, M.;  

3.3. Precise modeling of design patterns in UMLPrecise modeling of design patterns in UMLMak, J.K.H.; Choy, C.S.T.; Lun, D.P.K.;Mak, J.K.H.; Choy, C.S.T.; Lun, D.P.K.;

4.4. Instantiating and detecting design patterns: putting bits and pieces togetherInstantiating and detecting design patterns: putting bits and pieces togetherAlbin-Amiot, H.; Cointe, P.; Gueheneuc, Y.-G.; Jussien, N.;Albin-Amiot, H.; Cointe, P.; Gueheneuc, Y.-G.; Jussien, N.;

5.5. Design patterns-essentials, experience, Java case studyDesign patterns-essentials, experience, Java case studyPree, W.; Sikora, H.;Pree, W.; Sikora, H.;

6.6. A controlled experiment in maintenance: comparing design patterns to simpler A controlled experiment in maintenance: comparing design patterns to simpler solutionssolutionsPrechelt, L.; Unger, B.; Tichy, W.F.; Brossler, P.; Votta, L.G.;Prechelt, L.; Unger, B.; Tichy, W.F.; Brossler, P.; Votta, L.G.;

7.7. Precise specification and automatic application of design patternsPrecise specification and automatic application of design patternsEden, A.H.; Yehudai, A.; Gil, J.;Eden, A.H.; Yehudai, A.; Gil, J.;

Thank youThank you

Any Questions ????Any Questions ????