The PROMISE Core PAC (Core PEID Access Container) is a functional representation of a collection of PROMISE Core PEIDs. The Core PAC provides networking functionality to communicate with the backend via the PROMISE Data Services (middleware) layer. It implements a Device Interoperability Layer that must be supported by the Device Controller (DC) either in the middleware layer or as a distributed implementation.
In this way, the Core PAC hides the Core PEID’s specific implementation allowing uniform access from the backend layers. Note that neither the semantics nor the format of the content is addressed by the Core PAC definition.

The Core PEID may support different hardware platforms and PEID architectures, e.g. RFID readers, passive or active RFID tags, sensors, or tags with some computing power. The Core PAC interface is based on existing standards, and its implementation is language and platform independent.

The Core PAC defines the set of functionalities that allows access to one or more PEIDs. The Core PAC contains methods to access unique product identification, and the content of one or more PEIDs in a key/value fashion, methods to store content on one or more Core PEIDs, or security features like access control on the content or parts of the content of a Core PEID collection.

The adjacent figure shows the relationship of the Core PAC to other components in the PROMISE Architecture. The Core PAC is an interface between the device layer and the Device Controller. Depending on the specific PROMISE Data Services implementation, the Request Handling Layer (RHL) and the Device Handling Layer (DHL) may be either closely or loosely coupled. The shaded elements of the diagram designated "To be implemented" were a focus of development during the PROMISE Project.

The Core PAC Interface is described in detail in Volume 2 of the PROMISE Architecture Series "Architecture Reference: PROMISE Core PAC Interface".