The Science of Design

1. The Science of Design

2. What is Design? • Science vs. Engineering • Science teaches about natural things where engineering teaches about artificial things • Design vs. Engineering • Engineering used to be more about design but, like many other professional disciplines, became taught more as (applied) math and science • Design vs. Art • Design teaches process ofidea generation and artifactcreation • Where do you learn aboutdesign in Computer Science?

3. Representing Goals • Need for imperative logic • Paradoxes of using declarative logic for imperative statements • Optimization methods • Command variables represent inner design • Quantities of foods • Outer environment represented as probability distributions • Prices of foods, nutritional contents • Utility function computes goodness of particular set of command variables for expected context • Nutritional requirements, cost of diet

4. Satisficing • Some design settings overload computing requirements • Approximation algorithms • Many design settings do not enable enumerable goals and environmental variables • Consider the problem of being general manager for a basketball team • Extreme simple solution -> taking into account more information • Density of acceptable solutions determines how long search will take

5. Finding Alternatives • How to decide which potential designs to examine? • General Problem Solver (GPS) • Represent differences between current state and desired state • Determine actions likely to reduce that difference • Best-first search • Avoiding local maxima • Examine some non-best paths (e.g. simulated annealing) • Combine the features of known good alternatives (e.g. genetic algorithms)

6. Designing Design • But defining the problem is the problem • Coevolution of problem and solution spaces • Wicked problems (Horst Rittel) • Incomplete, contradictory, and changing requirements • Hierarchic resource allocation in design • Progressively design from very general to precise • Each step decides how much resources to put in subdesigns • Can decide how much effort to expend in collecting additional information in human design processes • Estimations of utility and future costs are difficult

7. Hierarchy as Outcome • Design decomposition • Semi-independent components • Alternative decompositions • How independent are components? • Design “style” may reflect process more than goals • Variety may be desirable end in itself • Designs are not independent (e.g. in architecture, business, evolution)

8. Representation of Design • Alternative representations and equivalence • Chess board problem • Number scrabble and tic-tac-toe • Changing the representationmay be part of design process • McGuckins example of heaters -> door • “solving a problem simply means representing it so as to make the solution transparent” • Does this assume perfect knowledge?

9. Topics in the Theory of Design • Evaluating alternatives • Optimal/satisficing algorithms • Formal logic of design • Heuristic search • Resource allocation for search • Hierarchic organizations • Representation of problems • “avoid cookbook approaches” • But where is the boundary?