Information hiding, encapsulation and modularity of software. But in software design, information hiding has been an important design principle ever since it was first discussed in a paper by david parnas in 1972. They realized that their education had taught them how to add to the worlds knowledge, but not how to build products. The system allows close cooperation between large numbers of inexpensive processors. Briefly describe one important lesson about modularity that the paper describes and that you think is still relevant today. Like most of the little academic knowledge of software that i. All processors share access to a single virtual memory address space. In the field of computer engineering, the process known as black boxing is usually associated with the 1972 paper by david parnas, on the criteria to be used in decomposing systems into modules.
For the functional programmer, consider hiding your data behind constructors and selectors, so that the programs are easier to modify, maintain, and grow over time. Usually nothing is said about the criteria to be used in dividing the system into modules. Parnas, a course on software engineering, proceedings of the acm sigcse technical symposium march 1972. The criteria used in arriving at the decompositions are discussed. On the criteria to be used in decomposing systems into modules on the criteria to be used in decomposing systems into modules. Parnas is a practical guide to key software engineering concepts that belongs in the library of every software. On the criteria to be used in decomposing systems into modules by d. Parnas communications of the acm, 1972 this paper discusses modularization as a mechanism for improving the flexibility and comprehensibility of a system while allowing the shortening of its development time. Pdf on the criteria to be used in decomposing systems into. On information hiding and encapsulation effective software. A lucid statement of the philosophy of modular programming can be found in a 1970 textbook on the design of system programs by gouthier and pont 1,10. A collection of papers on cm a multimicroprocessor computer. On the criteria to be used in decomposing systems into modules d. On the criteria to be used in decomposing systems into modules david l parnas, 1971 welcome back to a new term of the morning paper.
On the criteria to be used in decomposing systems into modules, cacm, dec. Citeseerx citation query designing systems programs. Does functional programming ignore the benefits gained from the on the criteria to be used in decomposing systems into modules data hiding. Pdf designing software for ease of extension and contraction. We can look at those through the lens of microservices too. Parnas 2 on the criteria to be used in decomposing systems into modules, d. I thought id kick things off by revisiting a few of my favourite papers from when i very first started this exercise just over two years ago. Morris techniques editor on the criteria to be used in decomposing systems into modules d. Sep 05, 2016 on the criteria to be used in decomposing systems into modules david l parnas, 1971 welcome back to a new term of the morning paper. Designing software for ease of extension and contraction.
How to decompose a system into modules hacker noon. For ease of maintenance, we would like the effect of each change to be localized to a single module. References 1 information distribution aspects of design methodology, d. Parnas professor of software engineering mcmaster university. The system is defined by a combination of microprograms and. Parnas developed the criteria and principles of modularization and information hiding while shaw extended his observations at new abstraction levels she constructed and described. Parnas, on the criteria to be used in decomposing systems into modules. The concept of informationhiding as a software design principle is widely. It is shown that the unconventional decompositions have distinct advantages for the goals outlined. Commonality and variability in software engineering. There i had the opportunity to have lunch with david parnas, one of the world pioneers in the field of software engineering.
Leading thinkers in software engineering have contributed short introductions to each paper to provide the historical context surrounding each papers conception and writing. A lucid statement of the philosophy of modular programming can be found in a 1970 textbook on the design of system programs by gouthier and pont 1, paragraph 10. There are no arbitrary limits on the number of processors, amount of memory or communication bandwidth. Information hiding, encapsulation and modularity are related. A technique for software module specification with examples. Parnas department of computer science carnegiemelion university pittsburgh, pa. Parnas seminal 1972 paper, on the criteria to be used in decomposing systems into modules, identified simplifying change as a critical criterion for modularizing software. Revealing the secrets of david parnas cs 61bl summer 2019. Parnas, on the criteria to be used in decomposing systems into modules, communications of the acm, vol. Parnas carnegiemellon university this paper discusses modularization as a mechanism for improving the flexibility and comprehensibility of a. A reference model for requirements and specifications. Computing has advanced significantly since this paper was written. This classic paper by parnas is the rst publication of the design concept known as information hiding. Does functional programming ignore the benefits gained from.
The process of developing good software is discussed and it is argued that writing programs, though obviously an essential step in the process, is only a small part of software engineering. On the criteria to be used in decomposing systems into modules. Parnas sets out three expected benefits of modular programming. On the criteria to be used in decomposing systems into modules david l parnas, 1971. Software engineering is discussed as a branch of engineering specialising in software intensive products. This paper will discuss that issue and, by means of examples, suggest some criteria which can be used in decomposing a system into modules. Abstract this paper discusses modularization as a mechanism for improving the flexibility and comprehensibility of a system while allowing the shortening of its development time. The effectiveness of a modularization is dependent upon the criteria used in dividing the system into modules. On the criteria for decomposing systems into modules. Mar 25, 2018 like most of the little academic knowledge of software that i. The beginning of software architecture publish your master. The unconventional decomposition, if implemented with the conventional assumption that a module consists of one or more subroutines, will be less efficient in most cases. Parnas carnegiemellon university this paper discusses modularization as a mechanism for improving the flexibility and comprehensibility of a system while. Hiding implementation details can be used in a very local setting to make a confusing expression understandable.
This paper discusses modularization as a mechanism for improving the flexibility and comprehensibility of a system while allowing the shortening of its development time. Software engineering programs are not computer science programs. Parnas is a practical guide to key software engineering concepts that belongs in the library of every software professional. The key idea is to design software modules around a single design decision that may change. Coupling 1,2the number of intermodule connections in software. Decoupling change from design proceedings of the 4th acm. An interview with dave parnas june 2018 communications of. Parnas carnegiemellon university this paper discusses modularization as a mechanism for improving the flexibility and comprehensibility of a system while allowing the shortening of its development time. Nov 25, 2012 there i had the opportunity to have lunch with david parnas, one of the world pioneers in the field of software engineering. Software engineering designing software for ease of extension and contraction 7 chain of programs a software system may do processing by passing data from one program to the next, with each doing its own bit of processing before passing it on to another program until it reaches the end of the line, which would be the output. Daniel hoffman is an associate professor of computer science at the university of victoria in british columbia. Parnas is the father of information hiding, a term he coined and which became popular through his seminal paper on the criteria to be used in decomposing systems into modules, published in 1972.
Information hiding for the functional programmer itnext. Parnas suggestion is to make an explicit list of design assumptions or characteristics that are likely to change in future versions of the system. I had heard and read many arguments in favour of modular programming. David parnas methods stanford university computer science. Evaluating programs, projects, and products, dorset. Aug, 2018 for the functional programmer, consider hiding your data behind constructors and selectors, so that the programs are easier to modify, maintain, and grow over time. A system design problem is presented and both a conventional and unconventional decomposition are described.
15 743 126 584 225 654 1407 779 493 1352 768 98 1598 612 1150 260 427 679 547 781 76 35 1263 861 819 681 1080 893 781 1243 813 839 1017 668 354