Smart grid interoperability depends on standards used by the diverse range of equipment and processes it is composed of. Standards also ensure against pre- mature obsolescence and support security implementation within the technologies they apply to. Utility PSA and equipment interface requirements have driven the need for a reference ICT standards architecture that can be mapped to the conceptual smart grid reference architectures to satisfy actor interaction requirements. The linkages between the standards architecture and smart grid conceptual architecture are use cases. These describe the series of events involving an actor and a technology or process, necessary to execute the intended smart grid capabilities and functions. In this sense, by forming the essential connection between a subject and its objective, the use case reflects the notion of the ‘‘subject-predicate- object’’ triple familiar within RDF notation. The scope for standards extension, modification or for new standards to be included in the reference architecture widens as the use cases for smart grid information and communications integration increase.
Use cases vary in the detail of their specification according to NIST by being either ‘‘prescriptive’’ or ‘‘descriptive’’ . The latter omits the specification for the implementation of the use case but describes the actor and functional requirements of the intended goal. Rigorous definition of use cases is therefore advisable to avoid confusion not only over the objective of an intended func- tionality but also to limit duplication of standards development effort. The refer- ence for defining smart grid use cases according to the EPRI IntelliGrid methodology is given in IEC Publicly Available Specification (PAS) 62559 . Its application process under M/490 is given in . Smart Grid use case repos- itories are being developed in the EU and the USA with one of the most mature managed by EPRI  (see also the NIST Interoperability Knowledge Base ).