Com S 362 Lecture Outline

Reading: Chapter 3 from Baldwin and Clark

The textbook is available on reserve in the library.

Recap:

Design: 

(n) a complete description of the structure of
an artifact and a possibly complete description of it's
functionality

Design parameters: smaller units of design

Hierarchical Design Parameters: Design parameters, 
certain choices of which bring new design 
parameters into existence in the design space.

Design interdependence: Symmetric dependence between 
design parameters

Design structure matrix: 
 - A square matrix
 - Design parameters as rows and columns
 - Initiating and resulting parameter in columns and rows.  
 - X's to denote hierarchies 
 - X's in symmetry to denote interdependencies  

Design Tasks: Deciding values of design parameter. 

Design Task structures often mirror design structure. 

Interconnected Design and Task Structures: The 
design structures in which there is a no 
decomposition to divide overall design into 
independent subdesigns.

Cycling through Design Parameters: For interconnected 
design and task structures, the designers must cycle 
through the tasks, searching for a combination of 
parameters that works. 

Some design structure idioms: Independent, sequential, 
hierarchical, and hybrid


Modularity: 

Module: A module is a unit whose structural elements 
are powerfully connected among themselves and 
relatively weakly connected to elements in other modules. 

On abstraction, information hiding and interfaces: A 
complex system can be managed by dividing it up into 
smaller pieces and looking at each one separately. 
When the complexity of one of the elements crosses a 
certain threshold, the complexity can be isolated by 
defining a separate abstraction that has a simple 
interface. The abstraction hides the complexity of 
the element; the interfaces indicates how the element 
interacts with the larger system.

Remember Parnas Information Hiding Principle: Every 
module in the second decomposition is characterized by 
its knowledge of a design decision which it hides 
from all others. Its interface or definition was chosen 
to reveal as little as possible about its inner 
workings. [Parnas 72, pp. 1056] 

Exercise: Read the original descriptions of the 
metaphors in Box 3.1 in the book.