Observation

An observation is a contextualized value produced by an observable acting on state. It is the form in which state becomes usable by an observer relative to a boundary.

An observation has:

A value, such as a scalar, array, vector, map, record, bytes, null, or another composite.
A shape or representation, such as a schema, projection, record layout, or optimized internal buffer.
A subject, source, or address that says what state the value was read from or derived from.
Optional context such as version, observer, source, and field-level lineage.

The value inside an observation is identity-free, version-free, lineage-free, and timeless. Observation metadata supplies attribution and provenance when correctness requires it.

Observations do not carry intrinsic occurrence time. Time and occurrence belong to events. An observation may carry a source version or observed-at metadata, but that is provenance or addressing, not the event occurrence itself.

When an entity is reconstituted, its current state is delivered as an entity-scoped observation. When an exogenous event arrives, its value can be observed and interpreted by an observer relative to a boundary. Commands are validated against observations of current entity state, related state, policy state, and environmental state. Queries request observations or values from state, projections, read models, or computations.

Entity state is a specialized observation whose subject is an entity. Non-entity observations may describe relations, projections, processes, policies, query results, aggregates, or runtime environment.

An event can be understood structurally as a time-bearing value. When the event is interpreted by an observer relative to a boundary, it may become an input event, command, endogenous event, output event, or ignored/rejected input.