This group of standards, created by the

OPC Foundation The OPC Foundation (Open Platform Communications, formerly Object Linking and Embedding for Process Control) is an industry consortium that creates and maintains standards for open connectivity of industrial automation devices and systems, such as ...

, provides COM specifications for communicating data from devices and applications that provide historical data, such as databases. The specifications provides for access to raw,

interpolated In the mathematical field of numerical analysis, interpolation is a type of estimation, a method of constructing (finding) new data points based on the range of a discrete set of known data points. In engineering and science, one often has a n ...

and

aggregate data Aggregate data is high-level data which is acquired by combining individual-level data. For instance, the output of an industry is an aggregate of the firms’ individual outputs within that industry. Aggregate data are applied in statistics, d ...

(data with calculations). OPC Historical Data Access, also known as OPC HDA, is used to exchange archived process data. This is in contrast to the OPC Data Access (OPC DA) specification that deals with real-time data. OPC technology is based on client / server architecture. Therefore, an OPC client, such as a trending application or spreadsheet, can retrieve data from an OPC compliant data source, such as a historian, using OPC HDA. Similar to the OPC Data Access specification, OPC Historical Data Access also uses Microsoft's DCOM to transport data. DCOM also provides OPC HDA with full security features such as user authentication and authorization, as well as communication encryption services. OPC HDA Clients and Servers can reside on separate PCs, even if they are separated by a firewall. To do this, system integrators must configure DCOM properly as well as open ports in the firewall. If using the Windows firewall, users only need to open a single port.

External links

OPC FoundationOPC Historical Data Access specification
{{List of Automation Protocols Industrial automation Computer standards Component-based software engineering

See also

External links