Glossary · Semantic interoperability and information models
Object model
Also known as: Instance model
German: Objektmodell
In modeling, an object model describes the objects (instances) of a system, their attribute values and the links between them, based on the classes or types defined for that system. The term is also used more broadly for the set of objects and interfaces a software system exposes.
- Information models
In one sentence
An object model describes a system's concrete objects, their attribute values and links, based on the classes or types defined for it.
Example
The object model of a bottling line lists filler F1, capper C1 and conveyor K3 as instances, with their parameters and the connections between them.
How it applies
- Engineering: Object models describe a specific plant or machine configuration: which devices exist, how they are connected and how they are parameterized. OPC UA address spaces and plant hierarchies are object models.
- Operation: Keeping the object model in sync with the real installation is essential; modifications on site must be reflected in the model.
- Documentation: Plant-specific documentation, such as equipment lists and parameter lists, is derived from the object model. Generating it from the model avoids inconsistencies.
Object model vs. class model
A Class model defines types, such as what a conveyor is and which attributes it has. An object model contains the actual conveyors of a plant with their values. Changes to the class model affect all objects of that class; changes to the object model affect only the instances concerned.