Datoms

Datoms are a fundamental concept in the database query language Datomic. A datom is the smallest unit of data in a Datomic database, representing a single fact. Each datom has four components: an entity ID, an attribute, a value, and a transaction ID. The entity ID uniquely identifies the subject of the fact. The attribute describes the type of relationship or property being asserted. The value is the actual data being stored for that attribute and entity. The transaction ID, also known as the 'tx' or 'time' component, indicates when the fact was asserted into the database.

Datomic's design is based on a data model that treats all information as a collection of datoms. This approach allows for powerful querying capabilities, including historical data retrieval and temporal reasoning. Because each fact is a distinct datom, the database can efficiently track changes over time. When data is updated or deleted, new datoms are asserted, rather than overwriting existing ones. This immutability of past data is a core principle, enabling a comprehensive audit trail of all database modifications. Queries in Datomic are formulated to retrieve specific sets of datoms based on their components, allowing for flexible and precise data access.