Harald E. Otto

From concepts to consistent object specifications: translation of a domain-oriented feature framework into practice

A steady increase in consumer demands, and severe constraints from both a somewhat damaged environment and newly installed government policies, require today’s product design and development to be faster and more efficient than ever before, yet utilizing even fewer resources. New holistic approaches, such as total product life cycle modeling which embraces all aspects of a product’s life cycle, are current attempts to solve these problems. Within the field of product design and modeling, feature technology has proved to be one very promising solution component. Owing to the tremendous increase in information technology, to transfer from low level data processing towards knowledge modeling and information processing is about to bring a change in almost every computerized application. From this viewpoint, current problems of both feature frameworks and feature systems are analyzed in respect to static and dynamic consistency breakdowns. The analysis ranges from early stages of designing (feature) concepts to final system implementation and application. For the first time, an integrated view is given on approaches, solutions and practical experience, with feature concepts and structures, providing both a feature framework and its implementation with sufficient system architecture and computational power to master a fair number of known consistency breakdowns, while providing for robust contexts for feature semantics and integrated models. Within today’s heavy use of information technology these are pre-requisites if the full potential of feature technology is to be successfully translated into practice.A steady increase in consumer demands, and severe constraints from both a somewhat damaged environment and newly installed government policies, require today’s product design and development to be faster and more efficient than ever before, yet utilizing even fewer resources. New holistic approaches, such as total product life cycle modeling which embraces all aspects of a product’s life cycle, are current attempts to solve these problems. Within the field of product design and modeling, feature technology has proved to be one very promising solution component. Owing to the tremendous increase in information technology, to transfer from low level data processing towards knowledge modeling and information processing is about to bring a change in almost every computerized application. From this viewpoint, current problems of both feature frameworks and feature systems are analyzed in respect to static and dynamic consistency breakdowns. The analysis ranges from early stages of designing (feature) concepts to final system implementation and application. For the first time, an integrated view is given on approaches, solutions and practical experience, with feature concepts and structures, providing both a feature framework and its implementation with sufficient system architecture and computational power to master a fair number of known consistency breakdowns, while providing for robust contexts for feature semantics and integrated models. Within today’s heavy use of information technology these are pre-requisites if the full potential of feature technology is to be successfully translated into practice.

Modeling with self validation features

One basic intent of feature-based modeling is to provide objects and operators which support the implementation of a complete and consistent description of a part in terms of its shape and related functional and technological information. Although feature-based methodology has matured to the point that results are being incorporated into commercial CAD systems, several problems still remain open. A key problem in feature-based modeling is how to maintain the consistent correspondence between the geometrical description of a feature and its related functional meaning (semantics) during the entire modeling process. Uncontrolled feature shape modification due to geometrical operations among aggregated features can affect the correct functionality of a modeled part. Within described work we propose to approach the problem of controlling feature semantics by using what we call self validation features: an entity concept developed to implement feature specifications replenished with self validation capabilities. Along with this new approach the traditional feature definition is extended in order to include a set of rules that allows for feature instances to control the consistency of their shape in respect to functionality associated. A feature-based modeling operation is then executed by computing within three steps as follows: feature instantiation, feature location and validated feature aggregation. A prototype testbed based on a self validation entity concept has been implemented integrating an in house developed feature system with a commercially available geometric modeling kernel. In order to realize a tight integration between feature semantics and shape representation an interfacing mechanism, based on an entity monitor, has been studied. Its functionality is partly supported by the attribute handling system of the integrated geometric modeling kernel. In the example section of the reported experimental work a selection of validation rules peculiar to some semantics aspects are evaluated and discussed.

A framework for structured data retrieval in LCA using feature technology

Obtaining the life cycle inventories (LCI) required for life cycle assessment (LCA) is often too expensive to be of use, as data is difficult to obtain and the amount of data is high. Integrating LCA into the design process can only be achieved by automating the extraction of LCI-relevant product data. Product models, that are used in product design, contain information relevant to the LCI and enabling structured access to that data reduces the amount of work for the LCA analyst by avoiding repeated determination and input of LCI data (data redundancy). This paper introduces a framework for a structured data retrieval in an LCA context through the use of feature technology. In a product model that includes a feature model, information on design features (e.g. geometry, dimensions) and manufacturing properties (e.g. material used, machining process applied) are included. Structured and efficient access to the LCI relevant data can be realized by a dedicated application program interface (API) bridging the gap between an LCA program and the product model. The characteristics and basic functionality of the API are described and the advantages of using an API are discussed. The basic idea of the framework is illustrated with a designed part.

Efficient Information Visualization in LCA

Background, Goal and ScopeA complete life cycle assessment (LCA) always requires several itemizations of goal/scope definitions, inventory analysis and impact analysis. This requires the retrieval and collection of inventory information on all processes with which a product or any part of it comes into either direct or indirect contact. As a result, the data required for LCA is vast, uncertain and, therefore, complex. Up until now, unfortunately, and as far as the authors are aware, there has not been much computer-assisted aid available from any of the systems currently used in either academia or industry to support any life cycle (LC) related data representation, other than the traditional methods of tables, xy-graphs, bar charts, pie charts and various 3-D variants of those which are difficult for humans to interpret.Main FeaturesBenefiting from the synergy of latest developments in both visualization techniques and computer technology, the authors are able to introduce a new information representation approach based on glyphs. These exploit the human perceptual capability for distinguishing spatial structures and shapes presented in different colors and textures. Within this approach, issues of representing life cycle related information at a glance, filtering out data so as to reduce the information load, and representation of data features, such as uncertainty and estimated errors, are targeted.ResultsAdvanced information visualization, the process which transforms and maps data to a visual representation, employs the glyphs rendered here to create abstract representations of multi-dimensional data sets. Different parameters describing spatial, geometrical and retinal properties of such glyphs, and defining their position, orientation, shape, color, etc., can be used to encode more information in a comprehensible format, thus allowing multiple values to be encoded in those glyph parameters. The natural function of glyphs, linking (mapped) data within a known context with the attributes that in turn control their visualization, is believed capable of providing sufficient functionality to interactively support designers and LCA experts performing life cycle inventory (LCI) information analysis so that they can operate faster and more efficiently than at present.ConclusionsWithin this paper, the first of a small series on efficient information visualization in LCA, the motivation for and essential basic principles of the approach are introduced and discussed. With this technique, the essential characteristics of data, relationships, patterns, trends, etc. can be represented in a much better structured and compact manner, thus rendering them clearer and more meaningful. It is hoped that a continuing interest in this work combined with an improved collaboration with industrial partners will eventually provide the grounds for translating this novel approach into an efficient and reliable tool enhancing applied LCA in practice on a broader base.OutlookMore technical details of the approach and its implementation will be introduced and discussed in the following papers, and examples will be offered demonstrating its application and first experimental translation into practice.

A reference kernel model for feature-based CAD systems supported by conditional attributed rewrite systems

According to the general design theory a design process is an evolutionary process which step by step transfers the model of the design object from the design specification to the design solution. In our framework, design object specification and iterating evaluation are performed over different contexts using featurebased design, and feature recognition/transmutation. These activities are integrated to achieve consistency between given design requirements and design objects. Features are used to relate elements of different domains, in order to represent design objects with shape and meaning within a context. The basic concept of topology and attributed entities is used to define a homogeneous architecture of the modeling space of our reference kernel. It is reflected in the uniform use and structure of an attributed feature graph, an attributed boundary representation, and a knowledge representation in form of conditional attributed rules. For design by feature and feature recognition we propose to use a conditional attributed rewrite system as a generative as well as a recognition device to represent knowledge of control and operationalization in a uniform way. Morphisms realize a bi-directional mapping between the entire modeling space of the reference kernel and an alphabet of attributed symbols, which together with rewrite rules define our rule-based design object specification. Knowledge representation for reflective functionality and strategies of design and recognition are specified with a conditional attributed rewrite system on a meta level. Central components of a prototype implementation, according to our proposed reference model kernel, will be introduced and discussed together with first results of modeled and evaluated objects.

Explicit 3D functional dimensioning to support design intent representation and robust model alteration

Design intent representation is a well-known issue in the MCAD domain, and is related to the readability, alterability, and usability of CAD models. The recent widespread introduction of functionality and commands in modern CAD systems, aimed at facilitating explicit modeling, introduces not only a new modeling paradigm supplementary to the feature-based approach, but also a new perspective on how the design intent can be captured and represented. Taking into account the traditional method of communicating design intent with functional dimensioning in mechanical drawings, in this paper a novel approach is presented, aimed at translating this traditional design intent representation from 2D into 3D. Objectives are directed towards the specification and implementation of dimensioning correspondence mapping and the identification as well as examination of shortcomings in current systems. This should help direct future improvements aimed at supporting 3D dimensioning within 3D explicit modeling systems.

Efficient information visualization in LCA: Application and practice

Aim, Scope and BackgroundAcquisition and analysis of huge amounts of data still pose a challenge, with few options available for solutions and support. Life cycle assessment (LCA) experts face such problems on a daily basis. However, data do not become useful until some of the information they carry is extracted, and most important, represented in a way humans can both recognize efficiently and understand and interpret as quickly as possible. Unfortunately, information representation techniques as used in this field are still based on traditional low-dimensional information spaces, featuring only a few basic choices to represent life cycle (LC) related data. We must part from those traditional techniques and shift to visual representations that are easier for us to understand due to the human capability for detecting spatial structures and shapes represented in different colors and textures. Then all the advantages of modern, advanced information visualization can be applied and exploited.Main FeaturesWith the introduction of a new glyph-based information representation and visualization approach to LCA, current issues of representing LC-related information efficiently at a glance are being tackled. These new techniques support reduction of information load by providing tools to select and summarize data, assist in making explicit and transparent data feature propagation, and provide a means of representing data errors and uncertainty. In this approach the human perceptual capability for easily and quickly recognizing and understanding graphical objects in different colors and textures is exploited for the design and application of highly structured and advanced forms of multi-dimensional information representation.ResultsNow in the example presented in this paper, OM-glyphs were used to represent LCA-related information for an industrial product and its compiled life cycle inventory under conditions normal for LCA. To demonstrate the application and benefits of the approach introduced, several different visualization scenarios were computed and presented. These were illustrated with a selection of generated glyph-based displays containing spherical glyph clusters for environmental items such as air pollutants and water pollutants, and inventory glyph matrices related to components and to LC phases. Where appropriate, to further aid understanding and clarity, displays were additionally shown with various orientations and in enlarged form. This is a functional feature of interactive 3D OM-glyph based information visualization that can be used in practice to efficiently navigate through displays while at the same time adjusting rendered scenes to the needs of the user at any given time. Due to the huge amount of data acquired and compiled, only a small fraction of the glyph-based displays could be shown, and, in consequence, only a fraction of the data properties, patterns and features available could be discussed in detail. However, it is believed that the basic principles and methods of this approach, as shown in a real application, could be clearly conveyed, and, most important, that the benefits and potential could be displayed in a convincing manner. This technology will support a marked increase in efficiency, speed and quality in LC information analysis.ConclusionsThis paper concludes our short series on efficient information visualization in LCA. A new approach to efficient information visualization has been introduced, together with its basic principles. This background was enriched with discussions on and further insights into technical details of the approach and the framework developed. The first practical examples were provided in the previous paper, demonstrating the mapping of LCA-related data and their contexts to glyph parameters. In this paper the application of the approach was presented using data for an actual industrial product. During the discussions, and with the various glyph-based displays shown, it could be convincingly demonstrated that all data features, trends, patterns, relationships, and data imperfections detected and examined, and sometimes traced, could be quickly and efficiently recognized in a short time. Even basic data features, such as small gaps in the data propagation of related values, could be easily seen using OM-glyphs. In the case of traditional data representation, using for example LCI tables, this would require the identification and comparison of several thousand numerical entries. As is the case with all new technology, however, it is still difficult to obtain the interest of the experts, and to convince them that such new ideas will eventually change the face of industry.OutlookA new, advanced and efficient information representation and visualization approach has been introduced to the LCA community. Hopefully, through this small series of papers, some interest will have been generated in the field of advanced information visualization. For the first time this area has been related to LCA, and some seeds for interdisciplinary research may have been sown. Now it is up to individuals, the experts in the various fields elated to those issues, to respond. The desired results will be stimulating discussions, an exchange of ideas, further initiated multilateral, interdisciplinary efforts, and improved collaboration between partners from academia and industry. At that point, efficient information visualization will finally have arrived at, and received, its deserved place within LCA.

Efficient information visualization in LCA: approach and examples

Aim, Scope and BackgroundThe data-intensive nature of life cycle assessment (LCA), even for non-complex products, quickly leads to the utilization of various methods of representing the data in forms other than written characters. Up until now, traditional representations of life cycle inventory (LCI) data and environmental impact analysis (EIA) results have usually been based on 2D and 3D variants of simple tables, bar charts, pie charts and x/y graphs. However, these representation methods do not sufficiently address aspects such as representation of life cycle inventory information at a glance, filtering out data while summarizing the filtered data (so as to reduce the information load), and representation of data errors and uncertainty.Main FeaturesThis new information representation approach with its glyph-based visualization method addresses the specific problems outlined above, encountered when analyzing LCA and EIA related information. In particular, support for multi-dimensional information representation, reduction of information load, and explicit data feature propagation are provided on an interactive, computer-aided basis.ResultsThree-dimensional, interactive geometric objects, so called OM-glyphs, were used in the visualization method introduced, to represent LCA-related information in a multi-dimensional information space. This representation is defined by control parameters, which in turn represent spatial, geometric and retinal properties of glyphs and glyph formations. All relevant analysis scenarios allowed and valid can be visualized. These consist of combinations of items for the material and energy inventories, environmental items, life cycle phases and products, or their parts and components. Individual visualization scenarios, once computed and rendered on a computer screen, can then interactively be modified in terms of visual viewpoint, size, spatial location and detail of data represented, as needed. This helps to increase speed, efficiency and quality of the assessment performance, while at the same time considerably reducing mental load due to the more structured manner in which information is represented to the human expert.ConclusionsThe previous paper in this series discussed the motivation for a new approach to efficient information visualization in LCA and introduced the essential basic principles. This second paper offers more insight into and discussion on technical details and the framework developed. To provide a means for better understanding the visualization method presented, examples have been given. The main purpose of the examples, as already indicated, is to demonstrate and make transparent the mapping of LCA related data and their contexts to glyph parameters. Those glyph parameters, in turn, are used to generate a novel form of sophisticated information representation which is transparent, clear and compact, features which cannot be achieved with any traditional representation scheme.OutlookFinal technical details of this approach and its framework will be presented and discussed in the next paper. Theoretical and practical issues related to the application of this visualization method to the computed life cycle inventory data of an actual industrial product will also be discussed in this next paper.

Algebraic interpretation of geometric tolerances for evaluating geometric uncertainties in solid modeling

Geometric tolerances specify the allowable limit of manufacturing imperfectness from the ideal design geometry. An actual feature is acceptable if it can be contained within the spatiaf tolerance zone. An unambiguous representation of the possible variationof the allowed actuaf feature is required for the development of computer-aided tolerancing systems. A general definition of the geometric tolerance is used as our basis, which includes the form, orientation, and position tolerances in the standards. Based on geometric characteristics of machined surfaces, an actual feature model is initiated as small position and orientation variations of boundary faces of the nominaf solid. The spatial constraint imposed on the acceptable feature is interpreted as a containment condition of the actual feature model by its corresponding portion of the tolerance zone. This condition is systematically derived in terms of Iincar inequalities based on the polyhedral approximation of the tolerance zone boundary. This paper discussed theoretical aspects of the method. Implementation of the system and evaluation of its applicability for analyzing machine parts with complex tolerance specifications are considered as following steps in our future work.

Error classification and recovery within CAD model reconstruction

With ever increasing demands from international markets and responding industries for a quick transfer as well as processing of CAD and product data between different computer aided applications, within as well as between a products life cycle stages, activities dedicated to the development and standardization of data representations and exchange formats are more critical than ever before. However, in practice, before complete standards and developed models and systems succeed and become reality, interim solutions are required to bridge certain gaps. One application field, requiring such interim solutions until robust methods are found, to correct error causing processes, is the exchange and consequent repair of geometric models. Due to subtle errors in geometric models and their representations, caused by design mistakes, programming errors or model evaluation failures, irrational behavior of CAD systems and other, post design related systems exchanging as well as accessing CAD data, are becoming a frequently observed situation, causing a severe break in the process of computer aided product development. To recover from such a rather undesirable situation, we propose an interim solution, aimed at bridging the gap between generation of corrupted CAD data and model exchanging post design applications. An approach, that is based on an error classification driven systematic recovery of corrupted CAD data being subject to model reconstruction. The approach taken includes a classification scheme for face adjacency errors, missing faces and curve adjacency errors for which dedicated individual methods and solutions were developed and related to. Practical work used to support as well as provide parameters for validation and assessment of proposed solutions was carried out using an implemented testbed, which is based on spatial model point distance tolerances driven face sewing. During experimental work exchange format used for model import/export were limited to IGES. Investigated models imported through these standardized data exchange formats were mainly taken from mechanical engineering.