INTERPRETATION IN DESIGN:

THE PROBLEM OF

TACIT AND EXPLICIT UNDERSTANDING

IN COMPUTER SUPPORT OF COOPERATIVE DESIGN

 

by

GERRY STAHL

 

B.S., Massachusetts Institute of Technology, 1967

University of Heidelberg, Germany, 1968

M.A., Northwestern University, 1971

University of Frankfurt, Germany, 1973

Ph.D., Northwestern University, 1975

M.S., University of Colorado, 1990

A thesis submitted to the

Faculty of the Graduate School of the

University of Colorado in partial fulfillment

of the requirement for the degree of

Doctor of Philosophy

Department of Computer Science

1993 

This dissertation for the Doctor of Philosophy degree by

Gerry Stahl

has been approved for the

Department of

Computer Science

by

Gerhard Fischer

Raymond J. McCall, Jr.

Date: August 5, 1993

Dissertation Committee:

Gerhard Fischer,                Computer Science                  (co-chair)

Raymond McCall,                  Environmental Design             (co-chair)

Clayton Lewis                       Computer Science

Mark Gross                           Environmental Design

Michael Eisenberg                  Computer Science

Wayne Citrin                           Electrical and Computer Engineering

Stahl, Gerry (Ph.D., Computer Science)

INTERPRETATION IN DESIGN:

THE PROBLEM OF TACIT AND EXPLICIT UNDERSTANDING

IN COMPUTER SUPPORT OF COOPERATIVE DESIGN

Thesis directed by Professors Gerhard Fischer and Raymond McCall

Abstract

This work analyzes the central role of interpretation in non-routine design. Based on this analysis, a theory of computer support for interpretation in cooperative design is constructed. The theory is grounded in studies of design and interpretation. It is illustrated by mechanisms provided by a software substrate for computer-based design environments, applied to a sample task of lunar habitat design.

Computer support of innovative design must overcome the problem that designers necessarily make extensive use of situated tacit understanding while computers can only store and display explicit representations of information. The automation techniques used for routine design are not applicable: techniques are needed to support creative, tacit human understanding with explicit computer representations.

The process by which designers transform their tacit preunderstanding into explicit knowledge is termed “interpretation”. Interpretation is necessary for solving design problems and collaborating with other designers. Considerable explicit knowledge is thereby generated in the natural course of designing. Often this knowledge includes the most valuable information that can be presented to designers who revisit these design projects or undertake similar projects in the future. If representations of this knowledge have been defined using computer-based design support systems, then the representations can be captured by these systems for the support of subsequent design work.

A theory of computer support for interpretation in design is presented in three stages. First, the role of interpretation in design is explored by reviewing descriptions of design by Alexander, Rittel, and Schön; by conducting a protocol analysis of lunar habitat design; and by applying Heidegger’s philosophy of situated interpretation. Second, this analysis of interpretation is extended to define a theory of computer support. The features of this theory—support for the situated, perspectival, and linguistic characteristics of interpretation—are used to evaluate previous work on software design rationale systems. Third, design principles are discussed for Hermes, a prototype hypermedia substrate for building computer-based design environments to support interpretation in tasks like lunar habitat design. The hypermedia integrates a perspectives mechanism and an end-user language to capture and modify representations of the design situation, alternative perspectives on design tasks, and terminology for conceptualizing design issues.

ACKNOWLEDGMENTS

The perspective on design methodology and the approach to computer support for design presented here grew out of the research of Raymond McCall of the School of Environmental Design, Gerhard Fischer of the Department of Computer Science, and other members of the Human-Computer Communication (HCC) group at the University of Colorado at Boulder. I have been privileged to work closely with Ray for three years as his graduate research assistant. My Hermes prototype began as a rewrite of his Phidias project, and incorporated much of its approach. Even where my ideas have gone off in new directions, they have been helped along by Ray's unbounded interest and unstinting assistance. For the same three years I have participated in the HCC research group led by Gerhard, particularly the weekly seminars on computers and design. Gerhard guided me from vague interests in theoretical issues to a coherent view and a concrete dissertation project, using his characteristic style that provides a model of non-directive critiquing at its most effective.

Clayton Lewis' courses on AI and interface design raised many of the concerns I have tried to address in my dissertation. The Hermes language benefited not only from Clayton's programming language evaluation methodology, but more from his personal perceptive analysis. Michael Eisenberg also contributed to my understanding of the language, bringing his understanding of (and support for) the role of languages in programmable applications. Each member of my committee contributed his own strong perspective to my work. However, I was able to rely on Mark Gross for balanced reality checks. Mark placed each draft I gave him in the broader view of AI and design practice, and wondered in a friendly but insistent way what these esoteric notions really had to do with making better habitats. Although I have tried to address many concerns of my professors and fellow graduate students, I have used Mark to represent my target audience: skeptical but informed and interested. Wayne Citrin played a similar role as reader of this dissertation.

While individual professors had specific effects on my work, the most pervasive influence was that of the HCC research group as a whole, which included about twenty graduate students during my stay. They built the systems, gave the presentations, and made fun of my ideas. A series of student reading groups on situated cognition was particularly important in helping me start to grapple with the ideas of Schön, Suchman, Winograd, Ehn, and Dreyfus. Research groups like this where people's very different perspectives are brought together under the constraints of shared work and common vocabularies exert pervasive influences that are impossible to acknowledge in detail. Nevertheless, I must single out my beta-testers, Tamara Sumner, Jonathan Ostwald, and Kumiyo Nakakoji, who relentlessly critiqued drafts of every chapter. Many of the ideas and formulations in the dissertation arose during reviews of those drafts with them and with Ray McCall. Special note should also be made of the dissertation work of Brent Reeves, Kumiyo Nakakoji, and Frank Shipman, which is closely related to the themes of this dissertation.

Implicit in this dissertation is the question about the relationship of AI to philosophy, which has intrigued me since my undergraduate days at MIT. In 1966 I attended a debate between my teachers, Marvin Minsky and Herbert Dreyfus. Convinced by Dreyfus' arguments that the approaches of AI were fundamentally flawed, I wondered what an AI based on Heidegger's philosophy would be like. What I am proposing now is a partial answer to that question, although one quite different from anything I could have imagined 25 years ago. For my understanding of Heidegger and hermeneutics I am indebted to Sam Todes, Ted Kiesel, Hans-Georg Gadamer, and members of the Frankfurt School of critical social theory.

Writing a dissertation is part of living a life. Accordingly, this dissertation owes its existence to Carol Bliss, my wife, without whom I would never have moved West to pursue this study. She both tolerated my long hours at the computer and enriched the remaining times.

Johnson Engineering (JE) of Boulder contributed generously the time and expertise of Designer Mike Pogue and Vice President John Ciciora. They provided the primary source of information about lunar habitat design, its needs, and its methods.

The research in providing computer support for the task of lunar habitat design was supported in part by grants to Ray McCall from the Colorado Advanced Software Institute (CASI) for 1990-91, 1991-92, and 1992-93 in collaboration with IBM and JE. CASI is sponsored in part by the Colorado Advanced Technology Institute (CATI), an agency of the State of Colorado. CATI promotes advanced technology education and research at universities in Colorado for the purpose of economic development.

Material from the following chapters has been previously published in different formats: Chapter 1 (Stahl, 1993a), Chapter 8 (Stahl, 1993b), Chapter 9 (Fischer, et al., 1993a, 1993b), Chapter 10 (Stahl, et al., 1992).

CONTENTS

ACKNOWLEDGMENTS 

CONTENTS 

LIST OF FIGURES 

LIST OF TABLES 

Introduction 

CHAPTER 1. OVERVIEW 

1.1. Understanding Interpretation  

1.2. The Methodology of Design  

1.3. The Example of Lunar Habitat Design  

1.4. The Analysis of Situated Interpretation  

1.5. Tacit and Explicit Knowledge in Design  

1.6. Consequences for a Theory of Computer Support  

1.7. Previous Software Systems for Design  

1.8. Hypermedia in the Hermes System  

1.9. Perspectives in Hermes  

1.10. The Hermes Language  

1.11. Conclusion  

Part I. Interpretation in Design 

CHAPTER 2. THREE METHODOLOGIES OF DESIGN. 

2.1. Alexander: the Structure of a Design Situation  

2.2. Rittel: Deliberating from Perspectives  

2.3. Schön: Tacit Knowing and Explicit Language  

CHAPTER 3. INTERPRETATION IN LUNAR HABITAT DESIGN. 

3.1. Situations of Privacy and the Problem of Representation  

3.2. Perspectives on Privacy 

3.3. Capturing the Language of Privacy  

CHAPTER 4. HEIDEGGER’S PHILOSOPHY OF INTERPRETATION 

4.1. Definition of the Situation as Basis for Tacit Understanding 

4.2. The Role of Shared Traditions and Personal Perspectives  

4.3. Interpretation as Explication in Language 

Part II. The Problem of Tacit and Explicit Understanding 

CHAPTER 5. GROUNDING EXPLICIT DESIGN KNOWLEDGE 

5.1. Applying Heidegger’s Philosophy to Design  

5.2. The Social and Human Grounding of Interpretation  

5.3. Transformations of Tacit to Explicit Understanding 

CHAPTER 6. A THEORY OF COMPUTER SUPPORT  

6.1. A People-Centered Approach  

6.2. Supporting Situated, Perspectival, Linguistic Interpretation  

6.3. A Model of Computer Support  

CHAPTER 7. RELATED COMPUTER SYSTEMS FOR DESIGN 

7.1. External Media for Design  

7.2. Perspectives for Deliberation  

7.3. Languages for Human Problem-Domain Communication  

Part III. Computer Support of Cooperative Design 

CHAPTER 8. REPRESENTING THE DESIGN SITUATION. 

8.1. A Computationally Active Medium for Designers  

8.2. Knowledge Representation in the Hermes Substrate  

8.3. Lunar Habitat Design Environments  

CHAPTER 9. INTERPRETIVE PERSPECTIVES FOR COLLABORATION 

9.1. A Scenario of Cooperation  

9.2. A Hypermedia Implementation of Perspectives  

9.3. Evolving Perspectives  

CHAPTER 10. A LANGUAGE FOR SUPPORTING INTERPRETATION 

10.1. An Approach to Language Design  

10.2 Encapsulating Explicit Mechanisms in Tacit Forms  

10.3 Defining Interpretive Critics  

Conclusion 

CHAPTER 11. CONTRIBUTIONS 

11.1 Contributions to a Philosophy of Interpretation  

11.2 Contributions to a Theory of Computer Support  

11.3 Contributions to a System for Innovative Design  

BIBLIOGRAPHY 

APPENDIX 

A. Programming Walkthrough of the Hermes Language  

B. Tacit Usage of the Hermes Language  

C. Explicit Structure of the Hermes Language  

LIST OF FIGURES

Figure 1-1. Transformations of tacit to explicit information 

Figure 1-2. The theory of computer support for interpretation in design 

Figure 1-3. Arranging sleep compartment bunks using Hermes 

Figure 2-1. A view of an issue-based information system in Hermes 

Figure 2-2. Four interpretations of the library 

Figure 3-1. Initial design of a lunar habitat layout 

Figure 3-2. A layout for living and working 

Figure 3-3. A private dressing area 

Figure 3-4. A privacy gradient 

Figure 3-5. Relative adjacencies based on functional relationships 

Figure 3-6. Required volume per crewmember as a function of mission duration 

Figure 4-1. Hermeneutic versus natural science approaches to design 

Figure 4-2. The two mainstreams of contemporary philosophy 

Figure 4-3. The network of references for tacit understanding of hammering 

Figure 4-4. The network of references that define Clara’s situation 

Figure 4-5. The network of references in lunar habitat design 

Figure 4-6. Two similar theories of breakdown 

Figure 5-1. Two different theories of breakdown 

Figure 5-2. The model of interpretation in design 

Figure 5-3. Successive transformations of knowledge 

Figure 5-4. A taxonomy of classes of information 

Figure 5-5. Successive transformations of information

Figure 6-1. Computer support for interpretation in design 

Figure 6-2. A model of cooperative interpretation and its computer support 

Figure 7-1. The multi-faceted architecture of Janus 

Figure 7-2. A layered architecture 

Figure 7-3. Growth in total and formalized information 

Figure 8-1. Layered architecture of Hermes 

Figure 8-2. The Hermes substrate object hierarchy 

Figure 8-3. A screen view of the Lhde interface 

Figure 9-1. Desi’s lunar habitat design 

Figure 9-2. The hierarchy of perspectives inherited by Archie 

Figure 9-3. Archie’s lunar habitat design 

Figure 9-4. Archie’s lunar habitat with its privacy ratings 

Figure 9-5. Output from the privacy check critic 

Figure 9-6. Output from the privacy display critic 

Figure 9-7. The privacy check critic applied to a list of all lunar habitats 

Figure 9-8. Output from the privacy gradient catalog expression 

Figure 9-9. Creating a new perspective 

Figure 9-10. Hierarchy of perspectives inherited by the team 

Figure 9-11. The result of modifying the virtual copy of a node 

Figure 9-12. An illustrative perspectives hierarchy 

Figure 9-13. Switching contexts to traverse a subnetwork 

Figure 9-14. Interface for merging existing information into a new perspective 

Figure 9-15. Three perspectives on a segment of design rationale 

Figure 9-16. Interface for demoting or promoting a node or subnetwork of nodes 

Figure 9-17. The layered architecture of design environments and Hermes 

Figure 10-1. A database of design rationale 

Figure 10-2. An example of hypermedia navigation 

Figure 10-3. Dialog boxes for defining DataList expressions 

Figure 10-4. Phrase structure of a Hermes critic rule 

Figure A-1. Family relations 

Figure A-2. Output from the academic advising application 

Figure A-3. A decision tree as virtual nodes 

LIST OF TABLES

Table 1-1. The structure of human interpretation 

Table 1-2. Computer-based mechanisms to support interpretation in design 

Table 1-3. Correspondences among the chapters 

Table 1-4. Syntactic classes of the Hermes language 

Table 4-1. The three aspects of interpretation 

Table 4-2. The three aspects of assertion 

Table 4-3. Increasing abstraction of the preconditions of understanding 

Table 10-1. Correspondence of language uses, operations and classes of terms 

Table 10-2. Major syntactic classes of the Hermes language 

Table 10-3. Examples of syntactic options for the Hermes language