Etatypes

Etatypes are a conceptual category used in data modeling and type systems to mark data elements whose origin or handling lies outside the core program logic. An etatype identifies data that comes from external sources, or that must undergo transformation before it can be used safely within the system.

The term arises in discussions about boundary-crossing software architectures, such as APIs, databases, and message queues, where distinguishing internal domain types from externally sourced representations helps clarify validation, marshaling, and security concerns.

An etatype carries metadata about provenance, transformation requirements, and validation constraints. Typical criteria include source (external versus internal), mutability, and the need for conversion steps or sanitization. Some designs annotate etatypes to enforce checks at compile time or runtime.

Examples include representing a JSON payload field mapped to an internal Customer type as an etatype until a transformation stage converts it to the internal domain model. A database row reference might be treated as an etatype to indicate lazy loading and separate validation.

Etatypes complement traditional types but introduce boundary-focused semantics. They can reduce errors by making provenance explicit; however, they also add design complexity. Critics argue that without standard definitions, etatypes risk duplication with data transfer objects or provenance metadata.

See also: data provenance, data validation, data transfer object, marshaling, type system.