Introduction

ISO 10303 is an International Standard for the computer-interpretable representation of product information and for the exchange of product data. The objective is to provide a neutral mechanism capable of describing products throughout their life cycle. This mechanism is suitable not only for neutral file exchange, but also as a basis for implementing and sharing product databases, and as a basis for retention and archiving.

Major subdivisions of this document are:

• geometry_schema;
• topology_schema;
• geometric_model_schema;
• scan_data_3d_shape_model_schema.

This document specifies the integrated resources used for geometric and topological representation. Their primary application is for explicit representation of the shape or geometric form of a product model. The shape representation presented here has been designed to facilitate stable and efficient communication when mapped to a physical file.

The geometry in clause 4 is exclusively the geometry of parametric curves and surfaces. It includes the curve and surface entities and other entities, functions and data types necessary for their definition. A common scheme has been used for the definition of both two-dimensional and three-dimensional geometry. All geometry is defined in a coordinate system which is established as part of the context of the item which it represents. These concepts are fully defined in ISO 10303 Part 43.

The topology in clause 5 is concerned with connectivity relationships between objects rather than with the precise geometric form of objects. This clause contains the basic topological entities and specialised subtypes of these. In some cases the subtypes have geometric associations. These specialised subtypes constitute the exclusive means of establishing direct associativity between geometric and topological elements at the integrated resource level. Also included are functions, particularly constraint functions, and data types necessary for the definitions of the topological entities.

The geometric models in clause 6 provide basic resources for the communication of data describing the precise size and shape of three-dimensional solid objects. The geometric shape models provide a complete representation of the shape which in many cases includes both geometric and topological data. Direct associativity between the geometric and topological data is achieved solely by specialised topological subtypes in clause 5. Included here are the two classical types of solid model, constructive solid geometry (CSG) and boundary representation (B-rep). Other entities, providing a rather less complete description of the geometry of a product, and with less consistency constraints, are also included.

The scan data shape models in clause 7 provide resources for the approximate representation of a 3 dimensional shape as a cloud of points.

The relationships of the schemas in this document to other schemas that define the integrated resources of ISO 10303 are illustrated in Figure 1 using the EXPRESS-G notation. EXPRESS-G is defined in ISO 10303-11.

The following schemas shown in Figure 1 are not found in this document, but are found as specified:

• measure_schema is found in ISO 10303-41;
• product_property_representation_schema is found in ISO 10303-41;
• representation_schema is found in ISO 10303-43.

The schemas illustrated in Figure 1 are components of the integrated resources.

• Figure 1 — Schema level diagram of relationships among ISO 10303-42 schemas and other resource schemas

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