Chapter 7FORMALISMS FOR NEGOTIATIONIN ENGINEERING DESIGNMichael J. Scott and Erik K. AntonssonProceedings of the8thInternational Conference on Design Theory and MethodologyASME, Paper Number 96-DETC/DTM-1525, (August, 1996)Abstract Engineering projects often undergo several design iterations before being com-pleted. Information received from other groups working on a project (analysis,manufacturing, marketing, sales) will often necessitate changes in a design. Theinteraction between different groups associated with a design project often takesthe form of informal “negotiation.” This form of interaction commonly ariseswhen engineering information is imprecise. The Method of Imprecision (MoI)is a formal method for the representation and manipulation of preliminary andimprecise design information. It provides a mechanism for the formalization ofthese informal negotiations. The nature and scope of informal negotiation inengineering is explored and discussed, and application of the MoI is illustratedwith an example.IntroductionEngineering design projects in industry commonly involve many differentwork groups or individuals. In addition to a division of labor by subsystems,there is a division of labor by engineering task. For example, the solid mod-eling and finite element analysis of an artifact may be handled by differentengineers. Production engineers form a group with its own set of concerns,reflected in the considerable literature on the importance of design for manu-facture (see [5] for a good bibliography). Finally, design engineers are ulti-mately responsible to their customers. The customers’ concerns are typicallyrepresented by management or marketing, who form yet another group with aninterest in the design process. The groups within an organization that partici-165166 IMPRECISION IN ENGINEERING DESIGNpate in a project, who are not necessarily all engineers, will be referred to hereas working groups.Interest in the issues that arise when so many different groups share thedesign task has led other researchers to explore concurrent engineering. [16],in particular, have pointed out the importance of the communication of set-based information between downstream and upstream processes. In this paper,we deal with situations of negotiation between working groups that arise in thecourse of a shared design task. Negotiation occurs whenever one workinggroup desires a change in work done by another working group. Often, adefining feature of a negotiation situation is that the two groups have differentviews of the design object or process. It is possible, however, for situationsthat are appropriately modeled as negotiation to arise where there is a single,agreed-upon view of the design. In general, this negotiation is highly informal.Other researchers, particularly in the artificial intelligence community, haveseen conflict and negotiation between agents as a crucial part of the design pro-cess. Several systems have been developed that attempt to model, incorporate,or handle conflict in design [2, 3, 6, 9, 13]. These projects will be discussedbelow.This paper was motivated by work done by the authors in collaboration witha US auto manufacturer and a material manufacturing research center. Wefound that the informal negotiations described above are common, so com-mon that informal negotiation appears nearly an automatic part of any designprocess. In most cases, it is not even recognized as negotiation, yet in someinstances the culture of negotiation is so highly developed that parties “cometo the bargaining table” with exaggerated estimates because they expect to be“bargained down.”Why is this sort of negotiation so prevalent? One reason is the fundamentalimprecision inherent in engineering design. Final designs are exact (includ-ing manufacturing tolerances), yet such precision is present only at the end ofthe design process. Engineers (and managers) routinely conduct analyses andmake decisions with imprecise quantities. As a design progresses, informationbecomes more precise, and it may become necessary to revise earlier estimates.Yet the preliminary decisions account for an overwhelming fraction of the totalcost of a design, with some studies citing figures up to 70% [17].Despite the ubiquity of imprecision in engineering design, there are fewtools for dealing with imprecise information. One such tool is the Methodof Imprecision (MoI) [18], a formal method for representing and manipulatinguncertainty in engineering design employing the mathematics of fuzzy sets.It has been shown that the MoI can be used to combine design informationusing a variety of different trade-off strategies [11, 15]. Other references havedeveloped the MoI for industrial application [8].Formalisms for Negotiation in Engineering Design 167Current work undertakes to use the structure of the MoI to formalize thepresently informal negotiation process. The mechanisms employed by the MoIfor the representation of uncertain or imprecise information are particularlywell-suited to the formal representation of the negotiation process. By for-malizing the negotiation process, design teams can promote a more completeexchange of information and have a mechanism to trace the history of a designthrough its iterations. The existence of a formal negotiation tool may facili-tate the inclusion of important performance goal and market information, thusallowing the incorporation of more relevant information into the early designstages.This paper discusses the context and importance of design negotiation inindustry, and demonstrates the application of the MoI to place negotiations ona formal basis.Examples of Negotiation in DesignThe following examples are not exhaustive, but they indicate the wide rangeof design negotiation situations:Unreachable target performance valuesOne example of design negotiation occurs when an engineer or engineeringgroup is given the task of designing a product to a target performance specifi-cation. When the product is a newer model of an existing product, the targetis often an incremental improvement over last year’s model. As an example,consider an automobile chassis, where an existing model has a torsional stiff-ness of 12,000 ft.-lbs./degree and this year’s requirement is to exceed that by10%. If the engineers are unable to reach the fixed target easily, they will re-turn to the manager who set the task and begin a negotiation process (indeed,this meeting may be scheduled long before