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.

This document specifies the representation_schema.

The representation_schema specifies the overall structure for representation. Collections of elements can be formed to act as the representation of some aspect of product data, such as a property of a product. Each element in such a collection is a representation item. An example of a property that can be represented is the shape of a product. The aspect or property that is being represented is not specified in this part of ISO 10303. Instead the subject of the representation is defined where the capabilities for representation are used in other parts of ISO 10303.

When representation items are collected to participate in a representation, they share a common context which is associated with the representation. This context is referred to as a representation context.

Not all elements of product data participate in representations. Those items which can participate in representations are defined to be representation items. Representation items are those elements that have complete meaning only when associated with a context. As an example, a point is a representation item which is only meaningful within a context (a coordinate space). In contrast, the name of a person is not a representation item because it has meaning separate from any context.

In addition to being an element of representation, a representation item can also support the definition of other representation items. This part of ISO 10303 allows for this distinction.

A collection of product data can contain numerous representation items, each participating in one or more representations. These representations can be related to form a structure which also relates the representation contexts. This structure can then be used to determine which representation items can be related to each other in a meaningful way. As an example, distance between points is only meaningful if the coordinate systems in which the points are defined can be related.

Representations that are unrelated in one context can be related in another. Consider the representation of the shape of a part and its components. The shape of each component can be represented as an independent concept, unrelated to the shape of the other components. In the context of the assembled part, however, the shapes of the components are related.

An aspect of product data can have zero, one, or multiple representations, none of which are the concept itself. For example, the shape of a part can be represented by a collection both of two-dimensional geometry and of constructive solid geometry. Either representation is an idealization of the shape.

Each representation is not necessarily a complete model of some aspect of product data, but it can represent a model of the aspect that is suitable for specific applications. Neither shape representation in the previous paragraph is necessarily a complete representation of the shape concept. Another shape representation might include tolerance information. Rather, each representation is suitable to some specific application’s view or approach.

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:

• application_context_schema is found in ISO 10303-41;
• product_definition_schema is found in ISO 10303-41;
• product_property_definition_schema is found in ISO 10303-41;
• product_property_representation_schema is found in ISO 10303-41.

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

• Figure 1 — Relationship of the representation_schema to the ISO 10303 integration architecture

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