cs427-16

cs427-16 - Modularity and Abstraction Alan Perlis: Epigrams...

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CS427 16-1 Modularity and Abstraction Alan Perlis: Epigrams on Programming 102. One can't proceed from the informal to  the formal by formal means.  http://www.cs.yale.edu/homes/perlis- alan/quotes.html Today:     http://www.acm.org/classics/may96/ http:// www.toa.com/pub/abstraction.txt
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CS427 16-2 Modularity “Modularity is the single attribute of software  that allows a program to be intellectually  manageable.” “Undermodularity or overmodularity should  be avoided.”
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CS427 16-3 What is a module? Procedure Class File Directory
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CS427 16-4 Functional independence Each module should do one thing - high  cohesion Each module should have a simple  interface - low coupling
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CS427 16-5 Coupling Measure of interconnection among  modules. The degree to which one module depends  on others. Minimize coupling.
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CS427 16-6 Cohesion Measure of interconnection within a  module. The degree to which one part of a module  depends on another. Maximize cohesion
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16-7 Cohesion Coincidental - ?? Logical - same idea
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cs427-16 - Modularity and Abstraction Alan Perlis: Epigrams...

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