objectdatabase

An object database, or object-oriented database management system (OODBMS), is a database system that stores data as objects defined by object-oriented programming languages. In an object database, objects encapsulate both data (attributes) and behavior (methods) and are identified by persistent references rather than by primitive keys. This alignment with in-memory objects aims to reduce impedance mismatch between application code and the stored data.

The data model follows object-oriented concepts such as classes, inheritance, encapsulation, and polymorphism. Objects can reference other objects, form object graphs, and participate in complex relationships. Identity is typically stable and independent of the object's attribute values, supporting long-lived references across transactions and sessions.

Storage and retrieval in an OODBMS focus on persisting object graphs with referential integrity and supporting transactional guarantees. Many systems offer ACID transactions, versioning, and caching. Query capabilities vary; some provide declarative query languages (such as the ODMG OQL) or language bindings that allow navigation of object graphs, while others emphasize direct navigation through object references or index-based access.

Schema considerations differ in practice. Some OODBMS are schema-based, requiring a predefined class structure, while others support schema evolution and schema-less usage. The trade-offs include tighter integration with object-oriented application code, potentially faster navigation for complex object structures, and reduced impedance mismatch, balanced against concerns about standardization, tooling maturity, and interoperability with relational or other non-object data stores.

Common use cases involve domains with rich object interrelationships, such as computer-aided design, simulations, multimedia, and complex data models. Alternatives include relational databases with object-relational mappers, document stores, and graph databases, each offering different strengths for persistence and querying.