Class definitions are groupings of plant objects and their associated attributes and properties. 
The high-level groupings of class definitions for P&ID are the following:
- Engineering Items. Includes equipment, nozzles, instrumentation, inline assets, and lines.
- Non Engineering Items. Includes items that cannot be purchased, or are not counted in reports (including flow arrows, gap, actuators, connectors, annotations, line breakers, and so on).
- Pipe Line Groups. Includes pipe lines.
- Signal Line Groups. Includes signal lines used with instruments.
The high-level groupings of class definitions for Plant 3D are the following:
- P3D Line Group. Includes line groups.
- Piping and Equipment. Includes equipment, pipe run components, and fasteners.
- Steel Structure. Includes structure members, railings, ladders, and so on.
You can modify existing class definitions.
Note: In P&ID only, you can also create new class definitions based on existing ones. For example, if your company uses a pump symbol that is not provided with the program, you can create your own customized pump symbol. When you create class definitions based on a family or parent, the new definition inherits the properties and settings of the family or parent.
You can modify the following properties for class definitions:
- Symbol or line settings (P&ID only). The name of the symbol or line style; the name of the block controlling the geometry that is displayed in the drawing after a component is inserted; the layer, color, linetype, linetype scale, and plot style; the lineweight of a component when it is inserted; and other settings that affect the insertion of a component or how a schematic line is drawn.
- Properties. The values assigned to a class definition to determine how a plant object looks and behaves in a drawing or model, and the values (such as default value, description, substitution, supported standards, and so on) that are attached to a plant object .
- Tag format. The information that comprises a unique tag for a plant object.
- Annotation. The text and symbol settings that annotate a plant object.