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  • AsianPLoP


    Asian Conference on Pattern Languages of Programs (PLoP) conference is a premier event for pattern authors and users to gather, discuss and learn more about patterns and software development in the Asia region as well as other regions. The purpose of AsianPLoP is to promote development of patterns, pattern languages, technologies and experiences of patterns primarily about software; however, these for domains outside of software are also welcome.Visit the Asian PLoP Official Site   Read More
  • EuroPLoP


    EuroPLoP is the premier European conference on patterns and pattern languages. EuroPLoP 2017 will be held again at Kloster Irsee, Bavaria, Germany. At this fantastic venue you will experience a creative and constructive atmosphere that inspires your work. Visit the EuroPLoP Official Site. Read the full story Read More
  • ScrumPLoP


    ScrumPLoP is a PLoP® conference. It will be a gathering of experienced Scrum practitioners, assembled with the goal of contributing to the body of pattern literature with proven practices. If you don't yet know what a PLoP conference is, read about what a PLoP is here. Visit the ScrumPLoP Official Site. Read More
  • Viking PLoP

    Viking PLoP

    VikingPLoP contains writer’s workshops for submitted pattern papers, focus groups, and other activities. The conference provides participants with the opportunity to share their experience about patterns and software. As with the PLoP series of conferences, our overall goal is to build a community of patterns' people. VikingPLoP especially encourages submissions related to embedded systems, however, also other pattern-related topics are very welcome. Read More
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Pattern Books

The Design Patterns Book Series showcases many patterns from PLoP conferences and leading experts in the patterns field.

See our Pattern Book Library filled with over 80 Pattern related books.

Patterns Resources

PLoP Conference News

All the C++ source code for the patterns in the book is available in a zip archive.

Note, this code is stripped directly from the original text and although it all compiles, (well almost all). Our goal was to have syntactically correct code, but not complete or executable code. We have played some tricks with #ifdefs, and introduced some dummy functions, so as to compile the pattern. These do not appear in the book.

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Pattern Name:

Name of pattern goes here

Note: use italics for all references to pattern names per Meszaros' pattern writing patterns. Delete this paragraph from actual pattern.

Aliases: Aliases (or none)


Give a statement of the problem that this pattern resolves. The problem may be stated as a question.


Describe the context of the problem.


Describe the forces influencing the problem and solution. This can be represented as a list for clarity.

  • Force one
  • Force two


Give a statement of the solution to the problem.

Resulting Context

Describe the context of the solution.


Explain the rationale behind the solution.

Known Uses

List or describe places where the pattern is used.

Related Patterns

List or describe any related patterns.


Describe the sketch, if needed.

Author(s): Author's name here or "as told to" for pattern mining

Date: Date string goes here, e.g., 3/1/96

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Pattern Source: Example: AG Communication Systems, Writers Workshop, etc.


Give a list of references cited in the pattern.

Keywords: Give a comma delimited string of terms used for searching.


Give an example implementation of the pattern. This can be code, pseudo code, etc. This section is optional.

Why are we, Erich Gamma, Richard Helm, Ralph Johnson, John Vlissides, called this? Who knows. Somehow the name just stuck. Hopefully like, the original Gang of Four, we have started a small cultural change with "Design Patterns..." And hopefully unlike the original Gang of Four we will not meet such an untimely end for our ("counter-revolutionary"?) ideas.

Erich Gamma is currently with a consulting group in Zurich whose name I (Ralph) can't recall. From 1993 to 1995, he was a software engineer at Taligent working on their object-oriented development environment. Erich was previously at UBILAB research laboratory of Union Bank of Switzerland. He was one of the architects of ET++, a portable C++ class library for developing interactive graphical applications. Erich has a Ph.D. in Computer Science from University of Zurich.

Richard Helm recently rejoined IBM to start the Australian branch of the Object Technology Practice. Prior to that, he was a technology consultant with DMR Group, an international information technology consulting firm. There he actively applied design patterns to the design of commercial systems. Prior to DMR, Richard was in the Software Technology department at IBM T.J. Watson Research Center investigating object-oriented design and reuse and visualization. Richard has numerous international publications, writes regularly in Dr. Dobb's Journal, and is a past OOPSLA program committee member. Richard has a Ph.D. in Computer Science from the University of Melbourne, Australia.

Ralph Johnson has been studying object-oriented technology and how it changes the way that software is developed for the past 10 years. He has been involved in the development of an object-oriented operating system (Choices), compiler (Typed Smalltalk), graphics editor framework (HotDraw), music synthesis system (Kyma), and is currently working on a framework for accounting. He is on the faculty of the Department of Computer Science at the University of Illinois and has helped organize several OOPSLA's, including OOPSLA'93 as program chair. He got his PhD from Cornell.

John Vlissides passed away November 24th, 2005. He was a researcher at the IBM T.J. Watson Research Center. His research interests included object-oriented design tools and techniques, application frameworks and builders, and program visualization. Before IBM, John was at the Computer Systems Laboratory at Stanford University. There he co-developed InterViews, a popular object-oriented system for developing graphical applications. John received his Ph.D. in electrical engineering from Stanford University.

This is the The Gang of Four's template. View and save this page's source from your web browser. It includes examples of useful HTML formatting commands.

Pattern Name (Scope, Purpose)

The pattern's name conveys the essence of the pattern succinctly. A good name is vital, because it will become part of your design vocabulary.


A short statement that answers the following questions: What does the design pattern do? What is its rationale and intent? What particular design issue or problem does it address?

Also Known As

Other well-known names for the pattern, if any.


A scenario that illustrates a design problem and how the class and object structures in the pattern solve the problem. The scenario will help you understand the more abstract description of the pattern that follows.


What are the situations in which the design pattern can be applied? What are examples of poor designs that the pattern can address? How can you recognize these situations?

  • An applicable situation



The classes and/or objects participating in the design pattern and their responsibilities.

Participant Name

  • Responsibility for what


How the participants collaborate to carry out their responsibilities.

  • [Collaboration]


How does the pattern support its objectives? What are the trade-offs and results of using the pattern? What aspect of system structure does it let you vary independently?


  1. A consequence bullet. Description of consequence


What pitfalls, hints, or techniques should you be aware of when implementing the pattern? Are there language-specific issues?


  1. An implementation Bullet. Description of Bullet

Sample Code and Usage

Code fragments that illustrate how you might implement the pattern in C++ or Smalltalk.

Program Listing

Known Uses

Examples of the pattern found in real systems. We include at least two examples from different domains.

Related Patterns

What design patterns are closely related to this one? What are the important differences? With which other patterns should this one be used?

  • Hillside Fellowship Award 2016
  • Security Patterns in Practice
  • PLoP Conference Proceedings
  • Asian PLoP
  • EuroPLoP

The Hillside Fellowship Award

Congratulations to Ralph Johnson and Richard Gabriel for being presented the first Hillside Fellowship award at the 2016 PLoP event at Allerton, PLoP 2016 .

Hilside Fellowship Award Recipients 2016

The Hillside Fellowship Program was established in 2016 to recognize members of The Hillside Group who have made exceptional contributions to the Hillside community and to the patterns community at large. The

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Security Patterns in Practice

Eduardo Fernandez's new book " Security Patterns in Practice: Designing Secure Architectures with Software Patterns " has been published.


It is the result of 14 years of producing security patterns with students and colleagues. Almost all of these patterns went through PLoP, EuroPLoP, AsianPLoP, or SugarLoafPLoP. Many of you have participated as shepherds or workshop commentators, the book

Read More

PLoP Conference Proceedings

After the PLoP Workshops, writers are encouraged to modify their papers and submit a final version. The final versions are collected and submitted to the ACM Digital Library. The versions are also available from the conference website.

Conference Proceedings (ACM Digital Library)

Some of the PLoP accepted papers have been published on the ACM Digital Library . The

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Asian PLoP

The premier Asian conference on
Pattern Languages of Programs

AsianPLoP solicits paper submissions written in both of English and Japanese; English papers and Japanese ones will be discussed in different sessions. Both practitioners from the industry and academics are invited to submit their papers. The conference solicits the papers for the following different sessions. Details can be found in Topics

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European Conference on Pattern Languages of Programs

EuroPLoP is a conference that explores, develops and celebrates patterns in software. As with PLoP in the US, the main focus of EuroPLoP will be a series of writer's workshops where pattern authors work together to improve their patterns.

In addition to these workshops there will be discussion groups, BOF sessions and

Read More


Learn More about Patterns


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