Constructed Representations and their Functions in Computational Models of Designing
CAADRIA 2000, pg.215-224
John S. Gero and Robert Saunders
This paper starts with an assumption of Schon and Wiggins that an important part of design are unexpected
accidents.
‘When we think of designing….as a conversation with materials conducted in the medium of drawing and
crucially dependent on seeing, we are bound to attend to processes that computers are unable—to
reproduce: the perception of figures or gestalts, the appreciation of qualities, the recognition of unintended
consequences of moves.”
(Schon, ’92.)
That was written eight years ago; Gero and Saunders argue that computation technologies have since
advanced enough to start to approach this level of comprehension and understanding of the design process.
They make a distinction between constructed representations and fixed representations; the essential
difference being that fixed representations are like CAAD drawings while constructed representations can
be interpreted on a number of levels of understanding. This notion implies that design is not representation
of what is, but an exploration of what might be.
“Constructed representations take advantage of the ambiguity of drawings to support the ‘suggestions of
what might be’ for the computational processes. Constructed representations are determined with respect
to current design goals, strategies and knowledge learned from previous similar experiences. Learning
plays an important role in the processes that construct representations.” (217)
Design is also linked to situation. This is to say that constructed representations can vary depending on the
focus of interest in discussions or development. They argue that this allows static design processes to be
sensitive to the design situation. Depending on the focus in the process, different representations can be
drawn from a single “fixed representation” (cad drawing or other static literal drawing) by manipulating the
constraints of a design problem. However, they argue that it can be difficult to choose which representation
to investigate further because importance of an issue vary from situation to situation.
Gero and Saunders offer “design emergence” as an alternative to “situatedness.” Design emergence “is the
recognition of unintended consequences” of the design process, as stated by Schon and Wiggins. Gero and
Saunders clarify their position by defining it as: emergence is the process of making implicit feature
explicit.
Design emergence can be seen as externalizing thoughts or conceptual models through drawing or any
other method so that they may be exposed to the situational world and can be seen afresh by the maker and
subsequently altered. It is method through which one may learn about something that was once implicit by
making it explicit (with attributes.)
The most notable thing about design emergence is that it is a method that creates forms rather than reducing
them. It expands the design space that one can work within and therefore could produce multiple results
rather than pointing to one. From a computational end, Gero and Saunders therefore argue that a program
must be able to monitor both the process and the product of design “in order to detect significant changes in
representation that indicate the addition of new knowledge.” (219) They propose a method of gauging
novelty of constructed representations.
Gero and Saunders “define the novelty of constructed representations as the combination of its newness and
its utility within a situation.” As a way to support emergence, novelty in creative design is anything
expands the design space. These are situations that could not have been predicted by the user based on
previous experience.
The paper concludes with a program they have written called “Sketch.” Sketch operates on four levels
based on drawings completed by the user.
Literal Syntactic Apprehension- This level analyzes the bitmap data of a drawing and makes
determinations of the forms on a literal level, such as shapes. These forms are then categorized by the
program by comparison against previously learned classifications. This classification system is
continuously updated by the program to provide better results as the process progresses.
Emergent Syntactic Apprehension- This level processes forms as emergent figures and patterns that may
not be explicitly stated. Edge conditions, maximal line conditions and bounded space are analyzed in this
process and “produces bitmap images suitable for further analysis to produce design actions for novel
emergent shapes.”
Semantic Appreciation- This process assigns qualities and judgements to the emergent shapes and
relationships. Transformed and original versions are compared against each other on a pixel-by-pixel
basis.
Novelty Detection- This level constructs new representations that lie between the perceptions and
“expectations of the consequences of design actions.” This method can also relate shapes constructed on
different levels to one- another.
personal notes:
the theory component of this paper is interesting and brings some specific points to computer-based design.
Creation is an fundamental part of design and a process that shouldn’t be forgotten.
The externalization process to make previously implicit things explicit is a compelling; Gero and Saunders
approach this differently than what I have by including it within the process itself and as something
changeable.
The last part about Sketch is confusing. It is never mentioned in the paper prior to its explanation and
never fully explained what it is. Larger moves of the program are explained before any indication of what
smaller moves trigger them is given.