EPICS PVAccess is used to provide the protocol and transport for the AIDA-PVA framework. EPICS PVData is used to provide the Normative Types functionality used for data encapsulation and standardisation.

Normative Types are a set of software designs for high-level composite data types suitable for the application-level data exchange between EPICS V4+ network endpoints. In particular, they are intended for use in online scientific data services. The intention is that where the endpoints in an EPICS V4+ network use only Normative Types, each peer in the network should be able to understand all the data transmitted to it, at least syntactically, and be able to take processing steps appropriate to that data.

AIDA-PVA uses NTTable, NTScalarArray and NTScalar Normative Types to represent its data. These are the types that clients will receive as responses to requests. It is the client's responsibility to unmarshal data from these structures.

Behind the scenes AIDA-PVA expects requests to be specified using an NTURI. Clients need to be able to create an NTURI to interact with AIDA-PVA.

See EPICS Normative Types for more information

Normative Type Usage in AIDA-PVA