CMU CS 15-675 Architectures for Software Systems Spring 1997

Design Guidance

Garlan & Shaw Questions on Readings for Lecture 17

Due: Wednesday, March 12, 1997

The papers:

[SG96]: Chapter 5
Design Spaces and Rules (from paper by Tom Lane)
Quantified Design Space (from paper by MSE students Asada et al)

[SC96]: A Field Guide to Boxology

[McC97]: Web Security: How Much is Enough?

Hints:

This material offers several views on how to make architectural decisions.

Lane studied user interfaces in order to organize information about design decisions. For our purposes, the important ideas are the design space based on a taxonomy of characteristics and the rules that relate characteristics of the problem to the architectural design decisions. Read section 5.1 with this in mind. In particular, do spend enough time on the user interface content to see what's going on, but do not spend a lot of time on the details. Asada, Swonger, Bounds, and Duerig were MSE students in 1991-2. After studying Lane's paper in this course in 1991 and Quality Function Deployment somewhere else, they developed QDS for their studio project.

McCarthy reports on Wylder's attempt to simplify the selection of security technology for the web.

Shaw and Clements offer some rules of thumb to show how the boxology classification could structure the advice; these are offered as evocative examples but not a full design method.

Questions:

  1. What is a "design space"?

    Consider the results delivered by Lane's system and by QDS. In each case you set up descriptions of the design alternatives. However, there are significant differences in the information they deliver, and consequently there are significant differences in the way the designer will interact with the two systems. Describe the major difference(s).

  2. From your own experience or readings in this course, give two rules of thumb for choosing an architecture that are not already covered in SC96. Cite your sources.

    Note: Your answers should be in the style of the models of SC96 -- and as brief.

  3. Lane and Wylder use somewhat different strategies to provide architectural advice. What is the major difference between them? (Ignore the differences in the domains; this is a question about the structure of their advice, not about the differences between user interfaces and security.)

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Modified: 03/07/97