Com S 362 Lecture Outline
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         INFORMATION HIDING

Reading:

[Parnas 72] Parnas, D. L. 1972. On the 
criteria to be used in decomposing systems 
into modules. Commun. ACM 15, 12 (Dec. 1972), 
1053-1058. 

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Overview of the lecture

- KWIC system
- Two designs for KWIC system
- Differences between the two designs
- Notion of design decision
- Changeable design decisions
- Information hiding principle
- Class Exercise: design of a specification 
  language infrastructure

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Example discussed in class: 

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Let us suppose that we are designing a 
16' X 16' life-size fabric game board.
This game board has various parts 
marked above, where pieces of different
colors and shapes are to be attached.

These pieces will change in future. 
For example, the rectangular section in
the top-left may be replaced with a 
circular section of a different color.

Furthermore, the board is so large that
we want to split this into pieces using
zips such that they can be zipped together
when needed.

Q: How will we design these seams i.e. 
 how should we go about putting the zip
 on the fabric ?