Design Computer

Supporting Situated Interpretation

Gerry Stahl

Department of Computer Science,

School of Environmental Design,

and Institute of Cognitive Science

University of Colorado

Boulder, CO 80309-0430

*****@**.********.***

large amounts of data. However, the problem is how to

Abstract

capture and encode information relevant to novel future

tasks and how to present it to designers in formats that

This paper discusses the role of interpretation in

support their mode of work.

innovative design and proposes an approach to provid-

A framework for clarifying the respective roles for

ing computer support for interpretation in design.

computers and people in tasks like lunar habitat design

According to situated cognition theory, most of a

is suggested by the theory of situated cognition. Several

designer knowledge is normally tacit. Situated

s

influential recent books (e.g., Sch n, 1983; Winograd

interpretation is the process of explicating something

& Flores, 1986; Suchman, 1987; Ehn, 1988; Dreyfus,

that is tacitly understood, within its larger context.

1991) argue that human cognition is fundamentally

The centrality of interpretation to non-routine

different from computer manipulations of formal

design is demonstrated by: a review of the design

symbol systems. These differences imply that people

methodology of Alexander, Rittel, and Sch n; a

need to retain control of the processes of non-routine

protocol analysis of a lunar habitat design session; and

design, but that computers can provide valuable

a summary of Heidegger philosophy of interpretation.

s

computational, visualization, and external memory aids

These show that the designer articulation of tacit

s

for the designers and support interpretation by them.

knowledge takes place on the basis of an understanding

From the viewpoint of situated cognition, the

of the design situation, a focus from a particular

greatest impediment to computer support of innovative

perspective, and a shared language.

design is that designers make extensive use of tacit

As knowledge is made explicit through the

knowledge while computers can only use explicit

interpretive processes of design it can be captured for

representations of information. This paper discusses the

use in computer-based design support systems. A

role of tacit understanding in designing, in order to

prototype software system is described for representing

motivate an approach to computer support of design. It

design situations, interpretive perspectives, and domain

focuses on three themes: (a) the need to represent novel

terminology to support interpretation by designers.

design situations; (b) the importance of viewing

designs from multiple perspectives; and (c) the utility

of formulating tacit knowledge in explicit language.

The Need for Computer Support

The following sections discuss how these three

themes figure prominently in analyses of interpreta-

The volume of information available to people is

tion in design methodology and in a study of inter-

increasing rapidly. For many professionals this means

pretation in lunar habitat design. Following a

that the execution of their jobs requires taking into

discussion of the tacit basis of understanding, the

account far more information than they can possibly

philosophy of interpretation defines interpretation as

keep in mind. Consider the lunar habitat designers who

the articulation of tacit understanding. Then

serve as a key example in this paper. In working on

consequences for computer support for interpretation

their high-tech design tasks, they must take into

are drawn, and they are illustrated by the HERMES

account architectural knowledge, ergonomics, space

system, a prototype for supporting interpretation in the

science, NASA regulations, and lessons learned in past

illustrative task of lunar habitat design.

missions. Computers seem necessary to store these

interpretation, representations were developed for

Interpretation in Design Methodology

describing pivotal features of the design situation that

had not been included in the original specification;

The centrality of interpretation to design can be seen in

perspectives were evolved for looking at the task; and

seminal writings of design methodologists. The

terminology was defined for explicitly naming,

following summaries highlight the roles of appropriate

describing, and communicating shared understandings.

representations of the design situation, alternative

The designers felt that a careful balance of public

perspectives, and linguistic explications of tacit

and private space would be essential given the crew s

understanding within the processes of interpretation in

long-term isolation in the habitat. An early design

design.

sketch proposed private crew areas consisting of a bunk

Alexander (1964) pioneered the use of computers

above a workspace for each astronaut. Space constraints

for designing. He used them to compute diagrams or

argued against this. The traditional conception of

patterns that decomposed the structural dependencies of

private space as a place for one person to get away was

a given problem into relatively independent

made explicit and criticized as taking up too much

substructures. In this way, he developed explicit

room. As part of the interpretive designing process, this

interpretations for understanding a task based on an

concept was revised into a reinterpretation of privacy as

analysis of the unique design situation.

a gradient along the habitat from quiet sleep quarters to

For Rittel (1973), the heart of design is the

a public activity area. This notion of degrees of privacy

deliberation of issues from multiple perspectives.

permitted greater flexibility in designing.

Interpretation in design is an argumentative process in

In another interchange related to privacy, the

the course of which an image of the problem and of the

conventional American idea of a bathroom was

solution emerges gradually among the participants, as a

subjected to critical deliberation when it was realized

product of incessant judgment, subjected to critical

that the placement of the toilet and that of the shower

argument (p.162). Rittel idea of using computers to

s

were subject to different sets of constraints based on life

keep track of the various issues at stake and alternative

in the habitat. The tacit acceptance of the location of

positions on those issues led to the creation of issue-

the toilet and shower together was made explicit by

based information systems.

comparing it to alternative European perspectives. The

Sch n (1983) argues that designers constantly shift

revised conception permitting a separation of the toilet

perspectives on a problem by bringing various

from the shower facilitated a major design

professionally trained tacit skills to bear, such as visual

reorganization.

perception, graphical sketching, and vicarious

In these and other examples, the designers needed

simulation. By experimenting with tentative design

to revise their representations for understanding the

moves within the tacitly understood situation, the

design situation. They went from looking at privacy as

designer discovers consequences and makes aspects of

a matter of individual space to reinterpreting the whole

the structure of the problem explicit. Certain features of

interior space as a continuum of private to public areas.

the situation come into focus and can be named or

The conventional American notion of a bathroom

characterized in language. As focus subsequently

was compared with other cultural models and broken

shifts, what has been interpreted may slip back into an

down into separable functions that could relate

understanding that is once more tacit, but is now more

differently to habitat usage patterns. Various

developed.

perspectives were applied to the problem, suggesting

new possibilities and considerations. Through

discussion, the individual perspectives merged and

Interpretation in Lunar Habitat Design

novel solutions emerged.

In this interpretive process, previously tacit features

As part of an effort at developing computer support for

of the design became explicit by being named and

lunar habitat designers, thirty hours of design sessions

described in the language that developed. For instance,

were videotaped and analyzed (see Stahl, forthcoming).

the fact that quiet activities were being grouped toward

The specified task was to accommodate four astronauts

one end of the habitat design and interactive ones at the

for 45 days on the moon in a cylindrical module 23 feet

other became a topic of conversation at one point and

long and 14 feet wide.

the terminology of a privacy gradient was proposed to

A protocol analysis of the designers activities

clarify this emergent pattern.

shows that much of the design time consisted of

processes of interpretation, i.e., the explication of

previously tacit understanding. As part of this

sketch a line, or how to look at a drawing and see the

The Tacit Basis of Understanding

rough relationships of various spaces pictured there.

The architect understands what it is to be a designer, to

Situated cognition theory disputes the prevalent view

critique a drawing, to imagine being a person walking

that all human cognition is based on explicit mental

through the spaces of a floor plan.

representations such as goals and plans. Winograd and

Heidegger defines the situation as the architect s

Flores (1986) hold that experts do not need to have

context including the physical surroundings, the

formalized representations in order to act (p.99).

available tools, the circumstances surrounding the task

Although manipulation of such representations is often

at hand, and the architect own personal or

s

useful, there is a background of preunderstanding that

professional aims. The situation constitutes a network

cannot be fully formalized as explicit symbolic

of significance in terms of which each part of the

representations subject to rule-governed manipulation.

situation is already meaningful (see Stahl, 1975). That

This tacit preunderstanding underlies people ability to

s

is, the architect has tacit knowledge of the situation as a

understand representations when they do make use of

whole; if something becomes a focus for the architect, it

them. Suchman (1987) concurs that goals and plans are

is perceived as already understood and its meaning is

secondary phenomena in human behavior, usually

defined by its relations to the rest of the situation.

arising only after action has been initiated: when

To the architect, a rectangular arrangement of lines

situated action becomes in some way problematic, rules

on a piece of paper is not perceived as meaningless

and procedures are explicated for purposes of

lines, but, given the design situation, it is already

deliberation and the action, which is otherwise neither

understood as a bunk for astronauts. The bunk is

rule-based nor procedural, is then made accountable to

implicitly defined as such by the design task, the shared

them (p.54).

intentions of the design team, the other elements of the

Philosophers like Polanyi (1962), Searle (1980),

design, the sense of space conveyed by the design, and

and Dreyfus (1991) suggest a variety of reasons why

so on indefinitely. This network of significance is

tacit preunderstanding cannot be fully formalized as

background knowledge that allows the architect to

data for computation. First, it is too vast: background

think about features of the design, to make plans for

knowledge includes bodily skills and social practices

changes, and to discover problems or opportunities in

that result from immense histories of life experience

the evolving design. At any given moment, the

and that are generally transparent to us. Second, it must

background is already tacitly understood and does not

be tacit to function: we cannot formulate, understand,

need to be an object of rational thought manipulating

or use explicit knowledge except on the basis of

symbolic representations.

necessarily tacit preunderstandings.

At some point the architect might realize that the

This is not to denigrate conceptual reasoning and

bunk is too close to a source of potential noise, like the

rational planning. Rather, it is to point out that the

flushing of the toilet. The explicit concern about this

manipulation of formal representations alone cannot

physical adjacency arises and becomes something

provide a complete model of human understanding.

important against the background of relationships of

Rational thought is an advanced form of cognition that

the preunderstood situation. Whereas a commonsensi-

distinguishes humans. Accordingly, an evolutionary

cal view might claim that the bunk and toilet were

theorist of consciousness such as Donald (1991) traces

already present and therefore their adjacency was

the development of symbolic thought from earlier

always there by logical implication, Heidegger proposes

developmental stages of tacit knowing, showing how

a more complex reality in which things are ordinarily

these earlier levels persist in rational human thought as

hidden from explicit concern. In various ways, they can

the necessary foundation for advanced developments,

become uncovered and discovered, only to re-submerge

including language, writing, and computer usage.

soon into the background as our focus moves on.

The most thorough formulation of a philosophical

In this way, our knowledge of the world does not

foundation for situated cognition theory is given by

consist primarily in mental models that represent an

Heidegger (1927), the first to point out the role of tacit

objective reality. Rather, our understanding of things

preunderstanding and to elaborate its implications. For

presupposes a tacit preunderstanding of our situation.

Heidegger, we are always knowledgeably embedded in

Only as situated in our already interpreted world can

our world; things of concern in our situations are

we discover things and construct meaningful

already meaningful in general before we engage in

representations of them. Situated cognition is not a

cognitive activity. We know how to behave without

simplistic theory that claims our knowledge lies in our

having to think about it. For instance, an architect

physical environment like words on a sign post: it is a

designing a lunar habitat knows how to lift a pencil and

sophisticated philosophy of interpretation.

significance; (b) preview or expectations of things in

The Philosophy of Interpretation

the world as being structured in certain ways; and (c)

preconception, a language for expressing and

Human understanding develops through interpretive

communicating.

explication. According to Heidegger, interpretation

In other words, interpretation never starts from

provides the path from tacit, uncritical

scratch or from an arbitrary assignment of

preunderstandings to reflection, refinement, and

representations, but is an evolving of tentative

creativity. The structure of this process of interpretation

preunderstandings and anticipations. One necessarily

reflects the inextricable coupling of the interpreter with

starts with sets of prejudices that have been handed

the situation, i.e., of people with their worlds. Our

down historically; the interpretive process allows one to

situation is not reducible to our preunderstanding of it;

reflect upon these preunderstandings methodically and

it offers untold surprises, which may call for reflection,

to refine new meanings, perspectives, and

but which can only be discovered and comprehended

terminologies for understanding things more

thanks to our preunderstanding. Often, these surprise

appropriately.

occasions signal breakdowns in our skillful, transparent

behavior, although we can also make unexpected

discoveries in the situation through conversation,

Computer Support for Interpretation

exploration, natural events, and other occurrences.

A discovery breaks out of the preunderstood

situation because it violates or goes beyond the network The theory of situated cognition and the philosophy of

of tacit meanings that make up the preunderstanding of interpretation stress how different human

the situation. To understand what we have discovered, understanding is from computer manipulations of

we must explicitly interpret it as something, as having arbitrary symbols. These theories suggest the approach

a certain significance, as somehow fitting into the of augmenting (rather than automating) human

already understood background. Then it can merge into intelligence. According to this approach, software can

our comprehension of the meaningful situation and at best provide computer representations for people to

become part of the new background. Interpretation of interpret based on their tacit understanding of what is

something as something is always a reinterpretation of represented.

the situated context. Representations used in computer programs must be

For instance, the lunar habitat designers discovered carefully structured by human programmers who

problems in their early sketches that they interpreted as understand the task being handled thoroughly, because

issues of privacy. Although they had created the the computer itself simply follows the rules it has been

sketches themselves, they were completely surprised to given for manipulating symbols, with no notion of what

discover certain conflicts among the interactions of these symbols represent. People who understand the

adjacent components, like the bunks and the toilet. Of domain must codify their background knowledge into

course, the discoveries could only occur because of their software rules sufficiently to make the computer

understanding of the situation, represented in their algorithms generate results that will be judged correct

drawings. The designers paused in their sketching to when interpreted by people. Only if a domain can be

discuss the new issues. First they debated the matter strictly delimited and its associated knowledge

from various perspectives: experiences of previous exhaustively reduced to rules, can it be completely

space missions, cultural variations in bathroom designs, automated.

technical acoustical considerations. Then they Many tasks like lunar habitat design that call for

considered alternative conceptions of privacy, gradually computer support do not have such strictly delimited

developing a shared vocabulary that guided their domains with fully catalogued and formalized

revisions and became part of their interpretation of knowledge bases. These domains may require

their task. They reinterpreted their understanding of exploration of problems never before considered,

privacy and represented their new view as a privacy assumption of creative viewpoints, or formulation of

gradient. innovative concepts. Software to support designers in

These themes of representing the situation, such tasks should provide facilities for the creation of

changing perspectives, and using explicit language new representations and flexible modification of old

correspond to the three-fold structure of interpretation ones. As the discussion of Alexander emphasized, the

in Heidegger philosophy. He articulates the

s ability to develop appropriate representations

preconditions of interpretation as: (a) prepossession of dynamically is critical. Because they capture

the situation as a network of preunderstood understandings of the situation that evolve through

processes of interpretation, representations need to be additional effort. The software should reward its users

modifiable during the design process itself and cannot for increasing the computer knowledge base by

adequately be anticipated in advance or provided once performing useful tasks with the new information, like

and for all. providing documentation, communicating rationale,

The concept of an objective, coherent body of and facilitating reuse and modification of relevant

domain knowledge is misleading. As Rittel said, non- knowledge.

routine design is an argumentative process involving

the interplay of unlimited perspectives, reflecting

differing and potentially conflicting technical concerns, The HERMES System

personal idiosyncrasies, and political interests.

Software to support design should capture these In Greek mythology, Hermes supported human

alternative deliberations on important issues, as well as interpretation by providing the gift of spoken and

document specific solutions. Furthermore, because all written language and by delivering the messages of the

design knowledge may be relative to perspectives, the gods. A prototype software system named HERMES has

computer should be used to define a network of over- been designed to support the preconditions of

lapping perspectives by which to organize issues, interpretation (a) by representing the design

rationale, sketches, component parts, and terminology. construction situation for prepossession, (b) by provid-

As Sch n emphasized, interpretive design relies on ing alternative perspectives for preview, and (c) by

moving from tacit skills to explicit conceptualizations. including an end-user language for preconception.

Additionally, design work is inherently communicative It supports tacit knowing by encapsulating (a)

and increasingly collaborative, with high-tech designs mechanisms for analyzing design situations using

requiring successive teams of designers, implementors, interpretive critics (Fischer, et al., 1993), (b) alternative

and maintainers. Software to support collaborative sets of information organized in named perspectives

design should provide a language facility for designers (Stahl, 1993), and (c) hypermedia computations

to develop a formal vocabulary for expressing their expressed in language terms (Stahl, et al., 1992). In

ideas, for communicating them to future collaborators, each of these cases, the hidden complexities can be

and for formally representing them within computer- made explicit upon demand, so the designer can reflect

executable software. An end-user language is needed upon the information and modify (reinterpret) it.

that provides an extensible domain vocabulary, is

usable by non-programmers, and encourages reuse and HERMES is a knowledge-representation substrate for

modification of expressions. building computer-based design assistants (like that in

Heidegger analysis of interpretation suggests that

s Figure 1). It provides various media for designers to

most of the information that would be useful to build formal representations of design knowledge. The

designers may be made explicit at some moment of hypermedia network of knowledge corresponds to the

interpretation during designing. One strategy for

accumulating a useful knowledge base is to have the

software capture knowledge that becomes explicit while

the software is being used. As successive lunar habitats for bunks?

are designed on a system, issues and alternative

deliberations can accumulate in its issue base; new

perspectives can be defined containing their own

modifications of terminology and critic rules; the

language can be expanded to include more domain discussion of issue;

What are the design considerations for bunks?

vocabulary, conditional expressions, and query

formulations. In this way, potentially relevant

information is captured in formats useful for designers,

because it is a product of human interpretation.

This is an evolutionary, bootstrap approach, where

the software can not only support individual design

projects, but simultaneously facilitate the accumulation

of expertise and viewpoints in open-ended, exploratory Figure 1. A view of the HERMES design environment,

domains. This means that the software should make it showing (left to right) a dialogue for browsing, a view of

easy for designers to formalize their knowledge as it the issue base, a critic message, a construction area, and

becomes explicit, without requiring excessive a button for changing interpretive perspectives.

design situation. Nodes of the knowledge Acknowledgments

representation can be textual statements for the issue

base, CAD graphics for sketches, bitmap images to This paper is indebted to Gerhard Fischer, Ray McCall,

illustrate ideas, sound for audio commentary, or Kumiyo Nakakoji, Jonathan Ostwald, and Tamara

language expressions for critics and queries. Sumner, who helped to focus it, and to the HCC

HERMES supports the collaborative nature of design research group at the University of Colorado generally,

by multiple teams through its perspectives mechanism. whose ideas and systems it tries to ground theoretically

This allows users to organize knowledge in the system and extend practically.

into over-lapping collections. Drawings, definitions of

domain terms in the language, computations for critic

rules, and annotations in the issue base can be grouped References

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approach to computer support for designers situated

interpretation in the information age.

Supporting Situated Interpretation

Gerry Stahl

Department of Computer Science,

School of Environmental Design,

and Institute of Cognitive Science

University of Colorado

Boulder, CO 80309-0430

*****@**.********.***

303-***-****

Abstract

This paper discusses the role of interpretation in innovative design and proposes an approach to providing

computer support for interpretation in design.

According to situated cognition theory, most of a designer knowledge is normally tacit. Situated interpretation

s

is the process of explicating something that is tacitly understood, within its larger context.

The centrality of interpretation to non-routine design is demonstrated by: a review of the design methodology of

Alexander, Rittel, and Sch n; a protocol analysis of a lunar habitat design session; and a summary of Heidegger s

philosophy of interpretation. These show that the designer articulation of tacit knowledge takes place on the basis

s

of an understanding of the design situation, a focus from a particular perspective, and a shared language.

As knowledge is made explicit through the interpretive processes of design it can be captured for use in

computer-based design support systems. A prototype software system is described for representing design

situations, interpretive perspectives, and domain terminology to support interpretation by designers.

For publication in the Proceedings of the:

Fifteenth Annual Meeting of the

COGNITIVE SCIENCE SOCIETY

A Multidisciplinary Conference on Cognition

June 18-21, 1993

University of Colorado at Boulder

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