Glossary · Semantic interoperability and information models
Class model
Also known as: Class diagram
German: Klassenmodell
In modeling, a class model describes the classes of a domain or system, their attributes, operations and relationships such as inheritance, association and composition, usually shown as a UML class diagram. It defines the types from which objects are created, not the individual objects.
- Information models
In one sentence
A class model describes classes with their attributes, operations and relationships, such as inheritance, usually as a UML class diagram.
Example
A class model defines a class Valve with attributes such as nominal diameter and position, and subclasses ControlValve and OnOffValve that inherit them.
How it applies
- Engineering: Class models structure software and information models. In automation, they appear in object-oriented PLC programming, OPC UA type hierarchies and AutomationML class libraries.
- Integration: Inheritance allows common properties to be defined once. Keep hierarchies shallow and meaningful; deep inheritance is hard to understand and to change.
- Documentation: Class diagrams are useful in developer and integration documentation. Explain the meaning of each class and attribute in text, not only in the diagram.
Class model vs. object model
A class model describes types and their structure. An Object model describes the individual objects (instances) and their links at a given point or for a given system. A class model says what a valve is; an object model lists valve V-101 and V-102 in a plant.