1.6 OTHER APPROACHES TO DESIGN

In recent years, an increased effort  has  been  directed  toward  a better  understanding  of design methodology and the  design  process.  Design  methodology  is  the  study  of the process of designing. One  goal  of this  research  is to define  the  design  process  in  suffi- cient  detail  to allow  it to be encoded  in a form  amenable  to execution  in a computer,   us- ing  "artificial   intelligence"   (AI).

Dixon[6] defines a design as a state of information which may be  in  any  of several forms:

...  words,  graphics,  electronic  data,  and/or  others.  It  may  be  partial  or  complete.   It ranges   from  a small  amount   of  highly  abstract   information   early  in  the  design  process to a very large amount of detailed information later in the process sufficient to perform manufacturing. It may include, but is not limited to, information  about  size  and shape, function, materials,  marketing,  simulated  performance,  manufacturing  processes,  toler- ances,  and  more.  Indeed,  any  and  all  information  relevant   to the physical   or  economic life  of  a designed   object  is part  of its  design.

He goes on to describe several generalized  states  of information  such  as the requirements state  which   is  analogous   to  our  performance specifications. Information    about  the physical concept is referred  to as the  conceptual  state  of information  and  is analogous  to our ideation phase. His feature  configuration  and parametric  states  of  information  are similar  in concept  to our detailed   design   phase.   Dixon  then  defines  a design  process   as:

The series of activities  by  which  the  information  about  the  designed  object  is changed from  one  information    state  to another.

Axiomatic Design

N. P. Suh[7] suggests an axiomatic approach to design in which there are four domains: customer domain, functional domain, physical domain, and the process  domain.  These represent a range from "what" to "how," i.e., from  a state  of defining  what  the  customer wants  through  determining   the  functions   required  and  the  needed  physical embodiment, to how a process will achieve the desired end. He defines  two  axioms  that  need  to be satisfied   to accomplish   this:

I    Maintain   the  independence    of the  functional  requirements.

2    Minimize   the  information  content.

The first of these refers to the need to create  a complete  and nondependent  set of perfor- mance specifications. The second indicates  that  the  best  design  solution  will  have  the lowest  information  content  (i.e.,  the  least  complexity).   Others  have  earlier  referred   to this  second  idea  as KISS,  which  stands,  somewhat   crudely,  for  "keep  it simple,   stupid."