computer science

Presentation–abstraction–control

Presentation–abstraction–control is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Presentation–abstraction–control rather than just read about it. In short: Presentation–abstraction–control (PAC) is a software architectural pattern. It is an interaction-oriented software architecture, and is somewhat similar to model–view–controller (MVC) in that it separates an interactive system into three types of components responsible for specific aspects of the application's functionality.

Key takeaways

Presentation–abstraction–control belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Presentation–abstraction–control to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Presentation–abstraction–control from memory before moving on to harder problems.

Reference excerpt

Presentation–abstraction–control (PAC) is a software architectural pattern. It is an interaction-oriented software architecture, and is somewhat similar to model–view–controller (MVC) in that it separates an interactive system into three types of components responsible for specific aspects of the application's functionality. The abstraction component retrieves and processes the data, the presentation component formats the visual and audio presentation of data, and the control component handles things such as the flow of control and communication between the other two components. In contrast to MVC, PAC is used as a hierarchical structure of agents, each consisting of a triad of presentation, abstraction and control parts. The agents (or triads) communicate with each other only through the control part of each triad. It also differs from MVC in that within each triad, it completely insulates the presentation (view in MVC) and the abstraction (model in MVC). This provides the option to separately multithread the model and view which can give the user experience of very short program start times, as the user interface (presentation) can be shown before the abstraction has fully initialized.

History PAC was initially developed by French computer scientist, Joëlle Coutaz in 1987. Coutaz founded the User Interface group at the Laboratoire de Génie Informatique of IMAG.

See also Action Domain Responder Hierarchical model–view–controller Model–view–presenter Model–view–viewmodel Presenter First PAC-Amodeus

Notes

References Coutaz, Joëlle (1987). "PAC: an Implementation Model for Dialog Design". In Bullinger, H.-J.; Shackel, B. (eds.). Proceedings of the Interact'87 conference, September 1–4, 1987, Stuttgart, DE. North-Holland. pp. 431–436. Buschmann, Frank; Meunier, Regine; Rohnert, Hans; Sommerlad, Peter; Stal, Michael (1996). Pattern-Oriented Software Architecture Vol 1: A System of Patterns. John Wiley and Sons. pp. 145–168. ISBN 978-0-471-95869-7. Calvary, Gaëlle; Coutaz, Joëlle; Nigay, Laurence (1997). "From Single-User Architectural Design to PAC*: a Generic Software Architecture Model for CSCW". In Pemberton, Steven (ed.). Proceedings of the ACM CHI 97 Human Factors in Computing Systems Conference, March 22–27, 1997, Atlanta, GA. pp. 242–249. Archived from the original on 2007-08-25. Retrieved 2006-05-24. Coutaz, Joëlle (1997). "PAC-ing the Architecture of Your User Interface" (PDF). DSV-IS’97, 4th Eurographics Workshop on Design, Specification and Verification of Interactive Systems. Springer Verlag. pp. 15–32. Markopoulos, Panagiotis (1997). A compositional model for the formal specification of user interface software (PDF). PhD thesis, Queen Mary and Westfield College, University of London. p. 26. Archived from the original (PDF) on 2006-05-30. Retrieved 2006-05-25. Avgeriou, Paris; Zdun, Uwe (2005). "Architectural patterns revisited – a pattern language" (PDF). Proceedings of 10th European Conference on Pattern Languages of Programs (EuroPlop 2005), Irsee, Germany, July 2005. pp. 1–39.

External links Architectural outline for the game Warcraft as it might be implemented using the PAC Architectural Pattern: Programming of the application PACcraft:Architecture (in French) Pattern:Presentation-Abstraction-Control (pattern description) PAC description in the Portland Pattern Repository WengoPhone is a free software VoIP application that is written using the PAC design pattern. description of PAC and motivation for use in WengoPhone. demonstration code, courtesy of the OpenWengo community. Cai, Jason; Kapila, Ranjit; Pal, Gaurav (July 21, 2000). "HMVC: The layered pattern for developing strong client tiers". JavaWorld. Retrieved 2020-07-18.

Illustrations

Worked examples

Example 1 — a first encounter with Presentation–abstraction–control

Start with the simplest possible case. Write down what Presentation–abstraction–control claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Presentation–abstraction–control before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Presentation–abstraction–control ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Presentation–abstraction–control

In research: Presentation–abstraction–control appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Presentation–abstraction–control in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Presentation–abstraction–control is common in secondary-school and first-year university syllabi. It links to neighbouring topics Human–computer interaction, Programming paradigms, Software architecture, so understanding it makes those chapters shorter.
In everyday life: Look for Presentation–abstraction–control outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Presentation–abstraction–control in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Presentation–abstraction–control means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Presentation–abstraction–control out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Presentation–abstraction–control in simple terms?

Why does Presentation–abstraction–control matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Presentation–abstraction–control?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Presentation–abstraction–control.