The IEC 61970-404 High Speed Data Access (HSDA) specification specifies a generalized interface for efficient exchange of data. The specification takes into account the latencies caused by a Local Area Network (LAN) providing efficient data exchange also over Local Area Networks. IEC 61970-404 is derived from the Object Management Group (OMG) Data Acquisition from Industrial Systems section Data Access (DAIS DA) specification. OMG DAIS DA relies on the OMG Data Access Facility (DAF) and OPC Data Access (DA) specifications. OMG DAIS DA is a Platform Specific Model (PSM) with CORBA as the platform and OPC DA is a PSM with Microsoft COM as the platform. IEC 61970-404 describes the functionality of these PSMs in a technology independent way (i.e.@ as a Platform Independent Model (PIM)). Hence it explains the functionality to a level that can be used to create additional PSMs or act as an introduction to existing PSMs@ i.e. DAIS DA and OPC DA. Implementers wanting an introduction to OMG DAIS DA and OPC DA shall read these documents. The HSDA interface is intended to interoperate with other IEC 61970 based interfaces. Hence@ it is possible to use information retrieved from an other interface to access the same information using this interface@ for example: ? object identifiers@ ?attribute names or identifiers@ ?class names or identifiers. Subclause 4.6 provides a generic mapping for the CIM classes and attributes. The way data is organized in a server implementing the HSDA interface can be seen by using the browse interfaces for data and meta data. It is also possible to use the data access interface directly without using the browse interfaces if the client has an a priori knowledge of object@ class and attribute identifiers. Object identifiers may be retrieved using data from other interfaces@ for example a CIMXML file or the IEC 61970-403 interface. Information on what classes and attributes are available will be described in IEC 61970-45X documents@ for example SCADA data@ State Estimator results etc. IEC 61970-1 provides the EMS-API reference model upon which this standard is based. In that reference model@ the terminology used in This part of IEC 61970 is introduced and the role of the CIS is explained. IEC 61970-401 provides an overview and framework for the CIS (IEC 61970-4XX) standards. The mapping of IEC 61970-404 to implementation specific technologies or PSMs is further described in a separate series of documents@ i.e. the future IEC 61970-5XX. For actual implementations@ the future IEC 61970-5XX@ OMG DAIS DA@ OMG DAF or OPC DA are used.