H. Craig Howard

Acquiring design knowledge through design decision justification

Currently design documentation rarely records the designers decision process or the reasons behind those decisions. This paper describes an effort to improve design documentation by having the computer act as an intelligent apprentice to the designer to capture the rationale during the design process. The apprentice learns about the features that make a specific case different from the standard. Whenever the designer proposes a design action that differs from the apprentices expectations, the interface will ask for the designer for justifications to explain the differences. Later queries for design rationale are answered using a combination of the apprentices domain knowledge and the designer-supplied justifications. The apprentice model is being implemented in a prototype system called ADD (Augmenting Design Documentation). The initial focus of the work is on HVAC (Heating, Ventilation, and Air Conditioning) design. Our starting point for implementing the apprentice model is observing how people develop HVAC system designs and then explain those designs.

Applying design-dependent knowledge in structural engineering design

This paper discusses the character of the design-dependent knowledge in a structural engineering context, describes two initial applications of case-based reasoning to component design, and presents a general paradigm for a knowledge-based design system integrating rule-based and case-based reasoning

Improving design and documentation by using partially automated synthesis

One of the products of engineering, besides constructed artifacts, is design documentation. To understand how design participants use documentation, designers and typical documentation users were interviewed and protocols were taken of them both creating and using design documentation. The protocols were taken from realistic projects of preliminary design for heating, ventilation, and air conditioning systems (HVAC). The studies of document creation and use revealed three important issues: (1) design participants not only look up design facts; they frequently access documents to obtain information about the rationale for design decisions; (2) the design rationale that they see often is missing from the documents; and (3) design requirements change frequently over a project life cycle so that design documents are often inconsistent and out of date. Recognizing these documentation issues in design practice, a new approach was developed in which documents are no longer static records, but rather interactive design models supporting a case. The feasibility of the approach was demonstrated by constructing a running system and testing it with designers on realistic problems. The costs and benefits of creating and using documentation of design rationale also were analyzed. In particular, the active documents approach was evaluated for a routine, preliminary design in domains where community practice is widely shared and largely standardized. The approach depends on the feasibility of creating a parametric design model for the design domain.

Recording and reuse of design strategies in an integrated case-based design system

Human designers often adopt strategies from previous similar cases to guide their search in new design tasks. We have developed an approach for automated design strategy capture and reuse. That approach has been implemented in DDIS, a prototype structural design system that uses a blackboard framework to integrate case-based and domain-based reasoning. Plans, goals, and critical constraints from user-selected previous cases are combined with case-independent reasoning to solve underconstrained parametric structural design problems. This article presents a detailed example of design strategy recording and reuse in base plate design for electrical transmission poles.

User interfaces for structural engineering relational data base

The needs of engineers in their interaction with engineering data bases are very different from those of their counter-parts in the business world. Business data base management system interfaces typically provide only a single mode of textual communication, usually a structured query language. However, in an idealengineering data base interface, an engineer would be able to define constraints, give examples, point at parts of pictures, and (sometimes) use several modes of communication simultaneously. The paper presents an example from an engineering design application to show how a traditional query language can be enhanced to accommodate the engineering needs. The paper further describes a conceptual approach for multimodal engineering data base interface combining multipurpose graphics, an engineering query language, and other interface methodologies in an engineering workstation environment.

Distributed AEC databases for collaborative design

The Architecture, Engineering and Construction (AEC) design process for a facility involves participation of many design specialists. These participants are architects, engineers (structural, mechanical and electrical) and contractors, who may be independent design professionals or design teams within an organization. From the viewpoint of information processing, two characteristic features distinguish the AEC design process from many other design domains. Firstly, there is a massive volume of design data involved in the design of each of its component specialties. Secondly, the specialization of the disciplines themselves warrant substantial autonomy. For design automation, this autonomy should be realized without sacrificing the collaborative nature of the multidisciplinary AEC design process. We propose autonomous AEC databases to deal with the first issue, and a global constraint maintenance mechanism for the second. Autonomous design databases can support the existing local applications in architectural, structural and mechanical engineering, and construction domains. However, a set of inter-disciplinary constraints needs to be enforced to ensure spatial and functional consistency of the design. A global constraint checking mechanism frees designers from the burden of keeping track of various design changes that may result in cross-functional conflicts. In this paper, we discuss the relevant issues for constraint management on distributed AEC databases. Although specific AEC examples will be used, the presentation is general enough to be applicable to other design domains, such as VLSI and manufacturing.