Software Design Patterns

10 Key excerpts on "Software Design Patterns"

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  eBook - ePub

  Software Engineering with UML

  • Bhuvan Unhelkar(Author)
  • 2017(Publication Date)
  • Auerbach Publications

    (Publisher)

  Fine granular classes take more effort to produce, but they are more reusable. This is because a large number of smaller-sized classes lend themselves to “better fit” in newer scenarios/requirements than larger-sized (coarse) classes. The flip side of this situation is that finer granularity designs require extra attention to quality, as there are a larger number of classes used for a given functionality. Furthermore, it is not only the classes themselves but also their relationships that need to be tested. Regardless of the case (fine or coarse), it is essential for system architects and system designers to keep in mind this vital concept in creating their object-oriented designs.

  Design Patterns in Software Design Engineering What Are Patterns?

  Patterns are recurring “thought processes” that are captured in abstractions. These “higher-level” abstractions can then be reused in newer designs without the designers having to undergo the same rigors as starting from scratch.

  Design patterns have provided one of the most popular approaches to reusing software and designs, especially in the context of object orientation. Due to the popularity of design patterns, other patterns of value have also appeared on the software engineering scene. These are:

  ■ Analysis patterns, which describe and model recurring phenomena during analysis in the problem space1

  ■ Design patterns, as discussed earlier, are recurring phenomena in solution space (Gamma et al., 1995)

  ■ Architectural patterns, which are recurring phenomena that occur as organizational constraints on the system being developed

  ■ Game patterns, which are recurring sociopsychological phenomena in software projects (Unhelkar, 2003, 2005)2 , 3

  Origins of Patterns

  The idea of patterns capturing design expertise originated with the architect Christopher Alexander. The Timeless Way of Building (1977)4

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  .NET 7 Design Patterns In-Depth

  Enhance code efficiency and maintainability with .NET Design Patterns (English Edition)

  • Vahid Farahmandian(Author)
  • 2023(Publication Date)
  • BPB Publications

    (Publisher)

  What are design patterns As can be seen from the title of the word "design pattern", it is simply a pattern that can be used to solve an upcoming problem. This means that the completed design is not a finished design that can be directly converted into source code or machine code. During the design and production of software, we face various problems in design Introduction to Design Patterns  7 and implementation, which are repetitive. Therefore, the answer to these often has a fixed format. For example, developing a feature to send messages to the end user may be necessary for software production. Therefore, a suitable infrastructure must be designed and implemented for this requirement. On the other hand, there are different ways to send messages to end users, such as via email, SMS, and so on. The mentioned problem has fixed generalities in most software, and the answer often has a fixed design and format. A design pattern is a general, repeatable solution to common problems in software design. Therefore, if we encounter a new issue during software production, there may be no pattern introduced for that, and we need to solve it without the help of existing practices. This needs to be solved by designing a correct structure. Using design patterns has several advantages: • Increasing scalability • Increasing expandability • Increased flexibility • Increase the speed of development • Reduce errors and problems • Reducing the amount of coding The important thing about design patterns is that they are not a part of the architecture of software systems, and they only provide the correct method of object-oriented coding. You can choose and implement the right way to solve a problem. GoF design patterns In the past years, Christopher Alexander introduced the design pattern. He was an architect and used patterns to build buildings. This attitude and thinking of Alexander made Eric Gama use design patterns to develop and produce software in his doctoral dissertation.

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  Handbook Of Software Engineering And Knowledge Engineering, Vol 2: Emerging Technologies

  Volume II: Emerging Technologies

  • Shi-kuo Chang(Author)
  • 2002(Publication Date)
  • World Scientific

    (Publisher)

  Once the pattern description is made public, other develop- ers can apply it in their projects and use effectively the knowledge and experience it contains. It is also of primary importance for developers to understand that using software patterns does not require knowledge of specific programming tricks or languages. Patterns only require a little extra effort in order to understand the recurring nature of solutions to specific problems, recognize instances of such problems in building specific software systems, and find a suitable way to apply already known solutions. The pay-off is definitely much larger that the extra effort: increased flexibility, modularity, and reuse of software, reduced development time, and efficient, elegant, and effective design solutions. 1.2. Classes of software patterns Patterns exist in several phases of software development. The software patterns community has first discovered, described and classified a number of design patterns. They name, abstract, and identify the key aspects of common design structures that are useful in creating reusable object-oriented design [18]. Design patterns identify the participating classes and objects, as well as their roles, collaborations, and distribution of responsibilities in recurring, stereotypical problems of object- oriented design. They are relatively low-level abstractions, in the sense that they are concerned with classes, their instances, and relationships that must be eventually implemented as programs. Note, however, that there are also lower-level patterns than design patterns. Novice practitioners in the world of software patterns will easily get used to the idea of software patterns starting from idioms, which are the patterns of source code levels [8,18].They express generally accepted conventions of certain program- ming languages or cultures, thus representing reuse in the small.

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  Software Paradigms

  • Stephen H. Kaisler(Author)
  • 2005(Publication Date)
  • Wiley-Interscience

    (Publisher)

  40 DESIGN PATTERNS 3 OVERVIEW OF DESIGN PATTERNS Design patterns are a recent software engineering problem-solving discipline that emerged from the object-oriented community. A design pattern is an abstract solu- tion to a problem. As we note later, design patterns arose from the work of Christopher Alexander, but also derive from the success of the Model-View-Controller (MVC) pat- tern used by Smalltalk-80 for GUI design. Today, there are many categories of design patterns across many technical and nontechnical disciplines. Design pattern definition has become a cottage industry in its own right. 3.1 A BRIEF HISTORY OF PATTERNS Although patterns have been used for hundreds of years in other disciplines (rug- making, cross-stitch, architecture, etc.), it is only within the past ten years that pat- terns have become a discipline to be studied within computer science. In 1987, Cunningham and Beck (Beck 1997) used Chris Alexander’s (1977, 1979) ideas to develop a small pattern language for Smalltalk-80. Smalltalk-80 was a good choice for this effort because it represented the only pure object-oriented programming lan- guage. By 1990, the Gang of Four had begun compiling a catalog of design patterns independently through work on their dissertations. In 1991, Bruce Anderson con- ducted the first Patterns Workshop at OOPSLA. In 1993, Kent Beck and Grady Booch organized the first meeting of a continuing series that is now known as the Hillside Group. In 1994, the First Pattern Languages of Program Design (PLoP) 41 Software Paradigms, By Stephen H. Kaisler ISBN 0-471-48347-8 Copyright © 2005 John Wiley & Sons, Inc. conference was organized (Coplien and Schmidt 1995). PLoP conferences have led to a continuing series of books that continue to enrich the patterns literature. Finally, in 1995, the Gang of Four published their design patterns book and, as they say, the rest is history. 3.2 WHY PATTERNS? Designing systems is a hard problem.

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  Hands-On Design Patterns with C# and .NET Core

  Write clean and maintainable code by using reusable solutions to common software design problems

  • Gaurav Aroraa, Jeffrey Chilberto(Authors)
  • 2019(Publication Date)
  • Packt Publishing

    (Publisher)

  Modern Software Design Patterns and Principles

  In the previous chapter, object-oriented programming (OOP ) was discussed in preparation for exploring different patterns. As many patterns rely on concepts in OOP, it is important to introduce and/or revisit these concepts.

  Inheritance between classes allows us to define an is-a-type-of relationship . This provides a higher degree of abstraction. For example, with inheritance it is possible to perform comparisons such as a cat is a type of animal and a dog is a type of animal . Encapsulation provides a way of controlling the visibility and access of details of a class. Polymorphism provides the ability to handle different objects using the same interface. With OOP, a higher level of abstraction can be achieved, providing a more manageable and understandable way to deal with large solutions.

  This chapter catalogs and introduces different patterns used in modern software development. This book takes a very broad view of what a pattern is. A pattern in software development is any solution to a general problem that software programmers face during development. They are built from experience on what works and what does not. Also, these solutions are trialed and tested by numerous developers in various situations. The benefit of using a pattern is based on this past activity both in not repeating the effort and in the assurance that the problem will be solved without introducing a defect or issue.

  Especially when taking technology-specific patterns into consideration, there are too many to cover in a single book so this chapter will highlight specific patterns to illustrate different types of pattern. We have tried to pick out the commonest and most influential patterns based on our experience. In subsequent chapters, specific patterns will be explored in more detail.

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  Handbook Of Software Engineering And Knowledge Engineering, Vol 1: Fundamentals

  Volume I: Fundamentals

  • Shi-kuo Chang(Author)
  • 2001(Publication Date)
  • World Scientific

    (Publisher)

  What is a design pattern precisely? Alexander et al [2] described, “Each pattern describes a problem which occurs over and over again in Our environment, and then describes the core of the so- lution to that problem, in such a way that you can use this solution a million times over, without ever doing it the same way twice”. The objective of DPs is to enable designers to easier reuse well-known and successful designs and architectures from experts’ experience. Expressing proven techniques as design patterns makes them more accessible to developers of new systems. DPs help you choose design Pattern-based Software Re-engineering 769 alternatives that make a system reusable and avoid alternatives that compromise reusability. DPs can even improve the documentation and maintenance of existing systems by furnishing an explicit specification of class and object interactions and their underlying intent. Put simply, design patterns help a designer get a design “right” faster [ 101. 2.1. The representation and classification of design patterns Properly documenting, representing and classifying design patterns can improve the effectiveness of their usages. In 1992, Coad [25] stated seven patterns applied in OOA and OOD. Gamma et al [ l O ] collected 23 design patterns and categorized these patterns into three classes: Creational Patterns, Structural Patterns and Behavioral Patterns. Their works provide a very handy reference book for software designers, particularly for beginners. Other researchers have tried to enhance the classification and their semantic relationships of DPs. Zimmer [33] identified three semantically different layers: (1) basic design patterns, (2) design patterns for typical software problems, and (3) application domain specific patterns. Tichy [33] categorized over 100 general- purpose DPs into nine catalogues: decoupling, variant management, state handling, control, virtual machines, convenience patterns, compound patterns, concurrency and distribution.

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  Java Enterprise Design Patterns, Volume 3

  Patterns in Java

  • Mark Grand(Author)
  • 2002(Publication Date)
  • Wiley

    (Publisher)

  He is a consultant who specializes in Distributed Systems, Object Oriented Design, and Java. He was the architect of the first commercial B2B e-commerce product for the Internet. C H A P T E R Introduction to Software Patterns 1 Software patterns are reusable solutions to recurring problems that occur during software development. For purposes in this book, we refer to soft- ware patterns simply as patterns. What makes a bright, experienced programmer so much more produc- tive than a bright but inexperienced programmer? Experience. Experience gives programmers wisdom. As programmers gain experience, they recog- nize the similarity between new problems and those problems that they have solved before. With even more experience, they recognize that the solutions for similar problems follow recurring patterns. Experienced programmers recognize the situations where these patterns apply and quickly draw on existing solutions without having to stop, analyze the problems, and then pose possible strategies. When a programmer discovers a pattern, it’s just an insight. In most cases, to go from a nonverbalized insight to a well-thought-out idea that the programmer can clearly articulate is surprisingly difficult. It’s also an extremely valuable step. When we understand a pattern well enough to put it into words, we are able to intelligently combine it with other patterns. More important, once put into words, a pattern can be used in discussions among programmers who know the pattern. That allows programmers to more effectively collaborate and combine their wisdom. It can also help to 1 avoid the situation where programmers argue over various solutions to a problem only to find out later that they were really thinking of the same solution but expressing it in different ways. Putting a pattern into words has an additional benefit for less experi- enced programmers who have not yet discovered the pattern.

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  Scientific Software Design

  The Object-Oriented Way

  • Damian Rouson, Jim Xia, Xiaofeng Xu(Authors)
  • 2011(Publication Date)
  • Cambridge University Press

    (Publisher)

  PART II SOOP TO NUTS AND BOLTS 4 Design Patterns Basics “There is one timeless way of building.” Christopher Alexander 4.1 Essentials Whereas code reuse played an important role in Part I of this text, design reuse plays an equally important role in Part II. The effort put into thinking abstractly about software structure and behavior pays off in high-level designs that prove useful independent of the application and implementation language. Patterns comprise reusable elements of successful designs. The software community typically uses the terms “design patterns” and “object- oriented design patterns” interchangeably. This stems from the expressiveness of OOP languages in describing the relationships and interactions between ADTs. Pat- terns can improve a code’s structure and readability and reduce its development costs by encouraging reuse. Software Design Patterns comprise four elements (Gamma et al. 1995): 1. The pattern name: a handle that describes a design problem, its solution, and consequences in a word or two. 2. The problem: a description of when to apply the pattern and within what context. 3. The solution: the elements that constitute the design, the relationships between these elements, their responsibilities, and their collaborations. 4. The consequences: the results and trade-offs of applying the pattern. Although there have been suggestions to include additional information in identi- fying a pattern, for example, sample code and known uses to validate the pattern as a proven solution, authors generally agree that elements 2-4 enumerate the three essential factors in each pattern. Alexander et al. (1977) referred to a slightly dif- ferent “three-part rule” as “a relation between a certain context, a problem, and a solution.” The current text takes a soup-to-nuts approach, providing the three essential elements followed by complete, compilable Fortran and C++ examples. We choose simplicity and clarity over speed and semantic power.

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  Pattern-Oriented Software Architecture, A System of Patterns

  • Frank Buschmann, Regine Meunier, Hans Rohnert, Peter Sommerlad, Michael Stal(Authors)
  • 2013(Publication Date)
  • Wiley

    (Publisher)

  The patterns in this book, and patterns written by others, already fulfill the first requirement—we are able to provide a sufficiently large and useful set of patterns. These patterns cover all ranges of scale, and address many problems in software architecture.

  Our pattern description template is also adjusted to the needs of a pattern system (see Chapter 1 , Patterns). It allows us to draw the ‘big picture’ for a pattern, to detail its concrete structure and dynamics, and to guide the implementation of the pattern described. Most importantly for pattern systems, our description template shows how a pattern is connected with other patterns, with which other patterns it can be refined and combined, which variants it exposes and which other patterns solve the same problem in a different way.

  However, a pattern system is more than just a collection of patterns described with a template. We must specify a useful organization scheme for patterns, and guide users in selecting patterns and building software systems with patterns. Finally, we must ensure that the pattern system is open to its own evolution.

  5.2 Pattern Classification

  The more patterns a pattern system includes, the more difficult it becomes to understand and use. If software developers must read, analyze and understand every pattern in detail to find the one they need, the pattern system as a whole is useless, even if its constituent patterns are useful. To handle the entirety of all patterns conveniently within a pattern system it is therefore helpful to classify them into groups of related patterns. A pattern classification schema that supports the development of software systems using patterns should have the following properties:

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  Design Science Research Methods and Patterns

  Innovating Information and Communication Technology, 2nd Edition

  • Vijay K. Vaishnavi, Vijay K. Vaishnavi, William Kuechler(Authors)
  • 2015(Publication Date)
  • CRC Press

    (Publisher)

  The resulting solution should be as good as the original solutions to the special cases of the general problem. If the solu-tion does not cover all the special cases or does not lead to solutions that are comparable to original existing solutions, then modify the abstractions and/or the level of abstraction. 4. Use the abstract concepts to develop a solution to the general problem. Consequences The pattern lets one capitalize on previous work and learn from it to develop a solution to a general problem. The pattern contributes to theory by devel-oping general concepts and other constructs that have general applicability. If successfully applied, the pattern can lead to contributions that have a broad impact. Suggestion and Development Patterns ◾ 251 Usage Example(s) 1. The research in Datta (1998) develops its solution by abstracting the prior work on software process modeling via grammar discovery; also see Chapter 13, p. 340. 2. Vaishnavi et al. (1997) use this pattern to derive the broad specifications of the smart object model; also see “An Example of ICT Design Science Research” in Chapter 2, “Pattern Usage in the Development of the Smart Object Paradigm” in Chapter 6, and Chapter 13, p. 312. Elegant Design Type Generalization Intent Design an artifact that is general and can be described functionally. Motivation DSR strives to create solutions that have general applicability and are not plagued by “ifs” and “buts.” Context/Applicability Your research involves creating an artifact, that is, something that does not exist in nature but must be created. You would like to construct a general design for the artifact, one that can be completely described in functional terms, that is, the properties of the artifact in terms of what it does rather than the details of the con-struction and organization of the artifact.

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