Rob H. Bracewell

Capturing design rationale

The subject of this paper is the Design Rationale editor (DRed). This is a simple and unobtrusive software tool that allows engineering designers to record their rationale as the design proceeds. DRed is one of the latest of many derivatives of the venerable IBIS concept. Thus it allows the issues addressed, options considered, plus associated pro and con arguments, to be captured in the form of a directed graph of dependencies. The research was conducted in close collaboration with, deployed, and tested in a major multinational aerospace company. The paper describes the main features of the tool, by means of a real design example from the company. It then examines the methodology and process by which the tool was researched, implemented and introduced into industrial practice. Finally, DRed is compared with other IBIS-based software, to identify and explain how it addresses problems that seem to have made earlier tools unsuitable for routine use by designers. Simplicity seems to be a key factor for real world acceptance of such tools.

Functional descriptions used in computer support for qualitative scheme generation—“Schemebuilder”

With increased pressures coming from global competition and requirements for greater innovation in product development, designers are hard pressed to deliver designs of higher quality and variety using a repertoire of technological options from different disciplines. This interdisciplinary product development approach has not only removed many of the traditional constraints to design but has now given designers a much wider freedom of choice as to the best solution to a design problem. The focus of this paper is a knowledge-based design environment called Schemebuilder, which is a comprehensive and integrated suite of software tools aimed at supporting the designer in the rapid development of product design models in the conceptual, through embodiment stages of design. Illustrated is the use of the software tools in the qualitative generation of alternative schemes, by application of stored working and decomposition principles in the development of a function-means tree-like information structure. With mechatronic product development as the main theme, this paper describes a closely integrated methodology that incorporates a bond graph approach to continuous-time energetic systems and high-level Petri nets for the rigorous description of discrete-time information systems. Additionally, a technique is suggested for the decomposition of free format statements of need into the rigorously defined design context and required functions, which form the starting point of the function-means development process.

DRed and Design Folders: A Way of Capturing, Storing and Passing On Knowledge Generated During Design Projects

This paper describes a software tool called DRed (the D esign R ationale ed itor), that allows engineering designers to record their design rationale (DR) at the time of its generation and deliberation. DRed is one of many proposed derivatives of the venerable IBIS concept, but by contrast with other tools of this type, practicing designers appear surprisingly willing to use it. DRed allows the issues addressed, options considered, and associated arguments for and against, to be captured graphically. The software, despite still being essentially a research prototype, is already in use on high profile design projects in an international aerospace company, including the presentation of results of design work to external customers. The paper compares DRed with other IBIS-derived software tools, to explain how it addresses problems that seem to have made them unsuitable for routine use by designers. In addition to the capture and presentation of the DR itself, the set of linked DR graphs can be used to provide a map of the contents of an electronic Design Folder, containing all the documents created by an individual or team during a design project. The structure of the knowledge model instantiated in such a Design Folder is described. By reprising a design case study published at the DTM 2003 conference, concerning the design of a Mobile Arm Support (MAS), the DRed knowledge model is compared with the previously proposed Design Data Model (DDM), to show how it addresses the shortcomings identified in the DDM. Finally the methodology and results of the preliminary evaluation of the use of DRed by aerospace designers are presented.Copyright

The retrieval of structured design rationale for the re-use of design knowledge with an integrated representation

Design knowledge can be acquired from various sources and generally requires an integrated representation for its effective and efficient re-use. Though knowledge about products and processes can illustrate the solutions created (know-what) and the courses of actions (know-how) involved in their creation, the reasoning process (know-why) underlying the solutions and actions is still needed for an integrated representation of design knowledge. Design rationale is an effective way of capturing that missing part, since it records the issues addressed, the options considered, and the arguments used when specific design solutions are created and evaluated. Apart from the need for an integrated representation, effective retrieval methods are also of great importance for the re-use of design knowledge, as the knowledge involved in designing complex products can be huge. Developing methods for the retrieval of design rationale is very useful as part of the effective management of design knowledge, for the following reasons. Firstly, design engineers tend to want to consider issues and solutions before looking at solid models or process specifications in detail. Secondly, design rationale is mainly described using text, which often embodies much relevant design knowledge. Last but not least, design rationale is generally captured by identifying elements and their dependencies, i.e. in a structured way which opens the opportunity for going beyond simple keyword-based searching. In this paper, the management of design rationale for the re-use of design knowledge is presented. The retrieval of design rationale records in particular is discussed in detail. As evidenced in the development and evaluation, the methods proposed are useful for the re-use of design knowledge and can be generalised to be used for the retrieval of other kinds of structured design knowledge.

Understanding how the information requests of aerospace engineering designers influence information-seeking behaviour

Engineering design activities rely heavily on the richness of knowledge and information available. In order to progress their tasks, designers undertake numerous searches to answer their information requests. A review of the literature on information seeking (IS) found that the role of the types of information request on source selection has been little investigated compared with that of the source itself, the seeker, the seeker–source relationship and the work context. This paper describes the empirical research that was carried out in collaboration with the aerospace group of a major power systems company to understand the relationship between information searches and information requests raised by designers involved in individual design tasks. The empirical part of the research consisted of participating in a design activity undertaken within the collaborating company and in conducting analytical studies with its designers. Two large data sets were gathered using a diary study and observations with shadowing. Based on the literature review and empirical research, a framework to describe how engineering designers access information was developed. The context of an information request, the request itself and the associated search were characterised through three groups of categories. Designers were found to raise requests to acquire information and to process information. The main sources used to answer these requests were colleagues, databases and drawings. In examining how sources are used, the research confirmed that designers generally prefer to source knowledge and information through informal interactions with their colleagues and demonstrated that colleagues are more often consulted to answer the requests to process information and documentary sources to answer the requests to acquire information. The results on the use of the media to communicate with colleagues indicated that face-to-face interactions are preferred to answer the requests to process information and phone calls to answer the requests to acquire information. Overall, the research emphasises the importance of unplanned face-to-face interactions in answering complex requests. Interpersonal communication emerges as a key resource for progressing design problems in a practical way, learning how to design and establishing social networks. For researchers, this study extends the existing knowledge by proposing to analyse and interpret engineering designers’ IS behaviour based on their information needs. Practitioners from current manufacturing organisations can use these findings to evaluate existing knowledge management efforts and subsequently undertake new interventions to improve the management of their knowledge and information.

Capturing an integrated design information space with a diagram-based approach

The Decision Rationale editor (DRed), an issue-based information system derivative, originally developed to support the capture of design rationale has progressively evolved into a tool to map an integrated information space-covering product planning, specification, design, and service. This article presents the research undertaken to enable this evolution and to test the application of the tool in industry. The work consisted of extending the notation and the functionality of the DRed tool in the service of new methods for information representation and developing a new approach to designing and its documentation by integrated diagrams. Thus far, the approach has been taught for two years and a half to engineering graduates involved in the training programme of the collaborating company. The application of the approach to an aerospace engineering design task is illustrated through a case study. The results of the evaluation have shown that creating large digital information spaces is feasible and delivers benefits to users.

The function analysis diagram: Intended benefits and coexistence with other functional models

Abstract Understanding product functions is a key aspect of the work undertaken by engineers involved in complex system design. The support offered to these engineers by existing modeling tools such as the function tree and the function structure is limited because they are not intuitive and do not scale well to deal with real-world engineering problems. A research collaboration between two universities and a major power system company in the aerospace domain has allowed the authors to further develop a method for function analysis known as function analysis diagram that was already in use by line engineers. The capability to generate and edit these diagrams was implemented in the Decision Rationale editor, a software tool for capturing design rationale. This article presents the intended benefits of the method and justifies them using an engineering case study. The results of the research have shown that the function analysis diagram method has a simple notation, permits the modeling of product functions together with structure, allows the generation of rich and accurate descriptions of product functionality, is useful to work with variant and adaptive design tasks, and can coexist with other functional modeling methods.

Engineering design and mechatronics - the Schemebuilder Project.

The paper describes the development of a software design aid for use at the conceptual stage of engineering design. It is intended for use in the design of mechatronic products but has wider potential uses. Early approaches were based on function structures and tables of options and the system that evolved allows the assembly of schemes linked by matching their input and output ports. A database of components is provided which can be accessed via different indexes and the designer can easily create and compare alternative schemes at the concept stage.A bond graph approach is used to define the interconnections between components. This allows correct port matching but also provides for future development such as constraint propagation through the design and links to simulation tools.

Characterising in Detail the Information Requests of Engineering Designers

This paper describes empirical research that was carried out in collaboration with the aerospace group of a major power systems company to characterise in detail the information requests of engineering designers. The research started by reviewing current classifications of information requests as well as the problem solving and reasoning processes. The data collection consisted of integrating ethnographical participation with a diary study and observations with shadowing. Two large data sets were gathered from the diary study and the observations. The literature review and the studies conducted in this project led to the development of six categories to classify information requests, namely objective, subject, response process, response type, direction of reasoning and behaviour type. The development of the categories was data driven. Each of the first four categories was designed to classify one characteristic of information requests. The final two categories were designed to be used together and to classify one additional characteristic of information requests. The paper discusses in detail the categories. The results of the quantitative analysis of the two data sets using the six categories are also presented. At a later stage of the research, a coding scheme to classify multiple characteristics of information requests was extracted from the six categories. The paper discusses the scheme with respect to current classifications. The implications of the research results to improve the support that can be provided to designers are also discussed and presented.Copyright

Synthesis based on function-means trees: Schemebuilder

This chapter describes the development of the Schemebuilder computer-supported methodology for the conceptual design of mechatronic and other multidisciplinary systems. This employed function-means trees, implemented using an artificial-intelligence-derived context management system, hierarchical schematic diagrams, and bond graph theory. Together, these allowed the generation of complete design schemes by creating, and forming combinations of, alternative partial design solutions. Quantitative dynamic simulation models were automatically created for the evaluation of the generated schemes. An illustrative example shows how the step-by-step application of Schemebuilder’s bond-graph-based rules were used to synthesise,from first principles, a novel and eventually commercially successful concept for a remote telechiric manipulator.