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An object data model describes a domain using objects or object types, their properties, and the relationships between them. In object-database contexts, it can also define object identity and operations. The term does not have one universally agreed scope, so it helps to distinguish the general modeling idea from a particular database model.
What is an object data model?
An object data model is a set of concepts for describing information as objects or object types, including the properties and relationships that matter in a domain. Depending on the modeling tradition, it may also make each object’s identity and behavior explicit.
For example, a library model might define Book, Author, and Publisher types. A book could have a title property and relationships to its authors and publisher. The model describes the domain structure; it is not, by itself, a decision about how a particular system stores that information.
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Objects and identity
An object represents an individual thing or fact in the domain. In object database models, an object is commonly described by its identity, state, and behavior. Some object database approaches assign an object a unique system-provided identifier, distinct from the values that describe its state.
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Types and classes
A type or class describes a category of objects and the properties or operations its instances share. A particular book is an object; Book is its type. Class and type definitions can form part of a database schema by specifying the structures used by instances.
Properties and relationships
Properties describe an object’s state. They may be attributes, such as a book’s title, or relationships to other objects, such as the book’s publisher. Relationships express associations between objects, while the model’s constraints determine which associations are allowed.
Operations and behavior
In a richer object database model, behavior is represented by operations that can be run on or by an object. This is not required in every use of the phrase “object data model”; some models focus on domain structure and relationships without defining executable operations.
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Inheritance and hierarchies
Some object models organize types into superclass and subclass hierarchies. A subclass can represent a more specific kind of object. Whether inheritance is supported, and what rules govern it, depends on the model being used.
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How is an object data model different from a database schema?
The object data model is the set of concepts used to describe information. A schema is a definition of the types and structures used for a database’s instances. In an object database, class or type definitions may contribute directly to that schema. In other settings, an object model may remain a conceptual description that is later translated into a different kind of schema.
Keep the modeling and implementation levels separate:
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- Conceptual model: identifies the kinds of things and relationships that matter in the domain.
- Logical model: expresses those ideas using a chosen data technology, such as tables and columns, object-oriented classes, or XML tags.
- Physical model: describes storage and deployment choices for a particular implementation.
The IEC 62264-2:2026 preview defines an object model as “a conceptual data model of the structure of data” and says that it does not prescribe how the structure must be implemented. The preview also describes UML models and definition tables as ways to represent information models. UML is therefore a notation for depicting a model, not the model itself.
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Why does the definition vary?
“Object data model” is used across related but distinct modeling traditions. A government-hosted technical reference on object database management systems describes objects with data structures and operations, unique object IDs, classes, instances, inheritance, and schemas. The ODMG 2.0 object database model likewise treats objects, literals, types, properties, operations, and schemas as part of its framework.
Those are specific object-database framings, not universal requirements for every object model. The government-hosted reference explicitly notes: “So far, there is no complete consensus on the object data model.” A useful definition should therefore state whether it means a general conceptual model of objects and relationships or a database model that also specifies identity and operations.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How UML fits into object modeling
UML can show object types, attributes, associations, roles, and hierarchies in a diagram. A diagram makes selected parts of a model easier to inspect, but it does not automatically determine all the model’s rules or how the system will store the data. A conceptual model can be represented in UML and then mapped to a logical schema and physical implementation.
Where this term is useful
Object data models are useful when a domain is naturally described through identifiable entities and their associations, or when a system needs to make object structure explicit. Before comparing two object models or choosing an implementation, check:
- Which domain concepts each model includes or omits.
- How it represents identity, properties, and relationships.
- Whether it supports operations, inheritance, and type constraints.
- How its conceptual structure maps to the target schema and storage.
- Whether the goal is a cross-application information model or a design tied to a specific technology.
Examples of documented object-model contexts
ODMG
ODMG is a historical object database standardization example. Its object model describes object and literal types, properties, operations, schemas, and language-independent object specifications. In the ODMG framing, an application’s object model defines particular types and becomes the database’s logical schema; this should not be assumed to describe every current database.
IEC 62264-2:2026
The IEC 62264-2:2026 preview uses object models in an enterprise-control context and discusses UML representation. It is useful for understanding the distinction between a conceptual model and its implementation, but conclusions about the standard should be limited to what the preview establishes.
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