Search Problems and Design Problems
In Notes on the Synthesis of Form Christopher Alexander begins with two types of problems: search problems and design problems. A search problem is a problem in which the space of possible solutions is well-known and finite. Because the space of possible solutions is tractable the problem can always be resolved by performing an iterative search over the different solutions in order to find the one with optimal fit. In design problems there is uncertainty or intractable difficulty in the solution space, such that an iterative solution is no longer possible. Alexander says that for this kind of problem a solution must be designed rather than discovered, making nonlinear and emergent approaches much likelier to succeed.
Alexanderâs project is to lay out a formal method of solving design problems. His first step is to characterize design problems as the search for fit between a âformâ and a âcontext.â In his initial examples of simple cases of designing for fit he discusses clear cases of calibration. The examples include leveling a metal surface and aligning metal filings to match a specific magnetic field. In both cases we can calibrate the form and context both in the âreal worldâ by a process of trial and error and mathematically. The mathematical descriptions of these cases, Alexander says, are possible because we can give a âcomplete unitary description of the demands made by the contextâ and the forces responsible for these demands are fully understood.
What does make design a problem in real world cases is that we are trying to make a diagram for forces whose field we do not understand.
For Alexander, design is calibration between a form and a context. When we attempt to calibrate a form in a context that we do not fully understand, we have to design.
A serious design problem is how we design our language. Itâs plausible to me that this is the most significant design problem that we face. The language we have constrains and modifies the problems weâre capable of recognizing and addressing, and our means of addressing them. One interesting question for another time is what contexts our languages are in and what good fit even means for languages and their contexts.
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