CCC and DCB Terminology

Orisun implements Command Context Consistency (CCC). Applications using Orisun need only CCC: query the events behind a decision, remember the observed context position, and save only while that same context remains current.

Dynamic Consistency Boundaries (DCB) describes a related event-store pattern. The shared idea is content-scoped optimistic consistency, but Orisun does not claim DCB specification compliance and does not expose a separate DCB mode or API.

Concept mapping

DCB concept	Orisun CCC concept
Event type	event_type on save; queryable as eventType in stored event data
Tags	Queryable JSON fields in event data
Query	Query.criteria used by GetEvents or GetLatestByCriteria
Append condition	SaveEvents.query.expected_position plus subsetQuery
Condition failure	ALREADY_EXISTS

This mapping is terminology for comparison, not a second implementation path. Use the CCC workflow and the EventStore API when building an Orisun application.

Important differences

• Condition semantics. A DCB append condition rejects when its query matches an event after the optional after position. Orisun instead requires the latest event matching subsetQuery to equal expected_position. A position later than the latest match is valid in DCB but fails Orisun's equality check.
• Query shape. DCB query items have first-class event-type and tag filters. Orisun criteria match JSON fields; event type is queried through the canonical eventType field.
• Match-all queries. The DCB specification requires a failIfEventsMatch query and permits that query to match all events. Orisun has no portable match-all CCC condition. Do not use empty criteria as a match-all query.
• Position representation. DCB requires unique, monotonically increasing positions but does not prescribe their representation. Orisun represents a position as (commit_position, prepare_position) and applications should treat the pair as an opaque ordering token.
• Boundary terminology. An Orisun boundary is a catalogued storage partition. A DCB consistency boundary is the event subset selected for a decision.

These differences are why the Orisun documentation describes the feature as CCC rather than advertising DCB compatibility.