next up previous contents
Next: 5.2 Object Summary Up: 5. Entity Reference Previous: 5. Entity Reference   Contents

5.1 Properties and the type heirarchy

Each model has zero or more properties associated with it; these properties specify characteristics such as an object's shape or a sensor's range. Models are organized into a heriarchy, with sub-types inheriting properties from their parent type. All passive environmental objects (boxes, pucks and bitmaps) are derived from a basic entity type and are referred to as objects. Similary, all sensors and actuator models are derived from a generic device type, and referred to as devices. The device type is itself derived from entity, so they devices inherit all the standrd entity properties.

Note that both the entity and device types are abstract (in C++ parlance) since they cannot be instantiated directly.