Charles M. Eastman

Geometric modelling: a survey

Abstract Computer programs are being developed to aid the design of physical systems ranging from individual mechanical parts to entire buildings or ships. These efforts highlight the importance of computer models of three dimensional objects. Issues and alternatives in geometric modelling are discussed and illustrated with comparisons of 11 existing modelling systems, in particular coherently-structured models of polyhedral solids where the faces may be either planar or curved. Four categories of representation are distinguished: data representations that store full, explicit shape information; definition languages with which the user can enter descriptions of shapes into the system, and which can constitute procedural representations; special subsets of the information produced by application programs; and conceptual models that define the logical structure of the data representation and/or definition language.

Parametric 3D modeling in building construction with examples from precast concrete

Buildings are complex products containing relatively large numbers of distinct parts that are collected in multiple assemblies for different design, analysis and production purposes. Modeling buildings in fully parametric 3D computer-aided design (CAD) systems offers numerous benefits in terms of productivity, the ability to rapidly generate design alternatives at different levels and elimination of errors that result from the disparity between different drawings in current practice. However, full realization of these benefits requires specialized functionality, including top-down modeling, objects with functional behavior, the ability to embed contextual design intent, automation of layout and detailing and appropriate management of similar objects. An effective system must provide such functionality while maintaining adequate response times. The requirements, features and performance have been examined as part of specification of a new 3D parametric CAD platform for the North American Precast Concrete Software Consortium (PCSC). They are described and discussed after a review of solid and parametric modeling, with examples from the domain of precast concrete construction.

Semantics of model views for information exchanges using the industry foundation class schema

The industry foundation classes (IFC) data schema is generic, designed to support the full range of model exchanges needed in the construction industry. For any particular working exchange for some sub-domain of building construction, a set of model view definitions (MVD) is required to specify exactly what information should be exchanged, and in what form and structure the IFC entities are to be used. Defining model view definitions requires principle decisions and workarounds because the IFC itself does not address a number of semantic issues comprehensively. Some of the issues identified and discussed include the typing of objects, instances, geometry, relationships, and rules, which are supported in the IFC schema, and the complexities of exchanging such information accurately between applications. This paper advances the idea of MVD Concepts as an object-oriented and modular mechanism for embedding semantic meaning in model views. We conclude that although the IFC product model schema is richly expressive, it lacks formal definition of its entities, attributes, and relationships. To achieve standardized and re-usable model views, further research towards a modular and logical framework based on formal specification of IFC concepts is recommended. This research is expected to impact the overall interoperability of applications in the building information modeling realm.

Automated space planning

This paper both reviews current procedures and introduces new ones for the automated generation of two-dimensional arrangements. General properties of the task and some sufficiency conditions for dealing with it are identified. The treatment of these properties in existing programs are reviewed. The task is also organized into its component decision rules. One exemplification of these rules is described which utilizes the sufficiency conditions and is implemented in the General Space Planner (GSP) program in operation at Carnegie-Mellon University [3], [4]. The performance of GSP in solving a set of spatial arrangement tasks is described and some future extensions outlined. A secondary purpose of this paper is to more fully introduce this problem domain to the artificial intelligence literature . Not only is it on interesting problem class now only the province of humans, but it has wide application. Throughout the presentation, both the commonalities and disparities of this task domain with other AI tasks are explicated.

A generic building product model incorporating building type information

Abstract Building product models are presented as an integrated representation for use in translating information between current and future design applications. Using an information model developed for design applications, we specify a Generic Building Model that represents both the physical and abstract information necessary to model basic knowledge about buildings and architecture. The Generic Building Model and its subsidiary concepts are reviewed. We show how it can incorporate building type information, and include the needs of various activities for comparison against the constructed form. We illustrate the models behavior by showing how it can be adapted to model information relevant to hospital design.

Representations for space planning

Problems involving the arrangement of objects in two- or three-space where the objective function primarily consists of derivatives of the distance between objects or their arrangement are called space planning problems. The representational requirements for this problem area are defined and compared with current computer graphic languages. Four alternative data structures that allow automated space planning are described and compared.

Information models for use in product design: a comparison

Abstract The paper reviews the reasons for the growing interest in product modelling and the application of data-modelling concepts to cad/cam development. The information needs for the design of products, as distinct from those for manufacturing, business and other applications, are articulated. Given these needs, five information models used in product modelling are reviewed: the entity-relationship model, niam, idef1x, express and EDM.

Out of STEP

This book will bring to many the memory of an interesting experiment carried out in the Army. This was an attempt to solve the difficulties of recalcitrant and anti-social youth?a problem which is rearing its head again in everyday life. The methods employed were carefully devised to trace the cause of delinquency and to help the individual to re-establish himself within a friendly, though disciplined, family. It may justifiably be said that present civilian problems cannot be compared, but the principles can be kept in mind.

A database supporting evolutionary product model development for design

This paper presents the facilities in the EDM-2 product modeling and database language that support model evolution. It reviews the need for model evolution as a system and/or language requirement to support product modeling. Four types of model evolution are considered: (1) translation between distinct models, (2) deriving views from a central model, (3) modification of an existing model, and (4) model evolution based on writable views associated with each application. While the facilities described support all for types of evolution, the last type is emphasized. The language based modeling capabilities described in EDM-2 include: (a) mapping facilities for defining derivations and views within a single model or between different models; (b) procedural language capabilities supporting model addition, deletion and modification; (c) support for object instance migration so as to partition the set of class instances into multiple classes; (d) support for managing practical deletion of portions of a model; (e) explicit specification and automatic management of integrity between a building model and various views. The rationale and language features, and in some cases, the implementation strategy for the features, are presented.

Database facilities for engineering design

As the complexity of engineering design projects increases and the objectives for their performance become more demanding, there is growing interest in integrated databases that support a broad range of applications and various forms of automated entry. This paper is a tutorial on the design and implementation of integrated design databases. It addresses a variety of functional issues, including subsystem integration, maintaining consistency among concurrent users and various system architectures.