IEC 62769-3-2021 Field device integration (FDI) – Part 3: Server.
4 Overview
The structure for an FDI Server is shown in Figure 1 .
FDI Servers that support connectivity with third-party FDI Clients shall support OPC UA. A vendor can provide both an FDI Server and one or more FDI Clients. In this case, the FDI
Clients can communicate with the FDI Server through proprietary protocols.
An FDI Server communicates with devices via Native Communication (see 7.2.1 ) and/or Communication Devices (see IEC 62769-7).
An FDI Server provides information to FDI Clients through an Information Model (see IEC 62769-5) as follows.
• The Information Model includes information about Device Types and Device Instances.
The information for a Device Instance includes offline data (engineering data), as well as online data (values from the physical device).
• The Information Model is created using information from FDI Packages. However, not all of the information in an FDI Package is reflected in the Information Model.
• Referential integrity of the Information Model is maintained using information from FDI Packages.
• FDI Packages can contain Attachments that contain device manuals and protocol-specific information (see IEC 62769-4). Those Attachments, including device manuals and protocol-specific support files, are exposed via the Information Model.
• FDI Device Packages contain information about device types (see IEC 62769-4). Each device type defined in a package is mapped to a distinct DeviceType node in the Information Model.
• FDI Profile Packages are used to provide interaction with devices for which an FDI Device Package does not exist (see IEC 62769-4).
• Multiple revisions of an FDI Package generate distinct DeviceType nodes in the Information Model (see IEC 62769-4).
FDI Packages contain digital signatures that allow an FDI Server to authenticate their contents (see IEC 62769-4). An FDI Server shall not use an FDI Package if the digital signature provided by the FDI Package is invalid.
An FDI Server shall verify the FDI Technology Version (see IEC 62769-1 ) of any FDI Package it uses to ensure the FDI Package is compatible with the FDI Server.
The resulting functional structure of an FDI server is described in Annex A.
5 Information Model
5.1 General
The FDI Server shall use the Device Definition of an FDI Package to maintain the Information Model.
The Device Definition can contain conditional expressions. Conditional expressions are used when a certain aspect of the Device Definition is not static but rather is dependent on the state of the device. Whenever the online or offline values of a Device Instance are modified, the FDI Server shall re-evaluate the relevant conditional expressions and modify the
Information Model accordingly.
The evaluation of conditional expressions can invalidate variables in the Information Model.
The FDI Server shall change the AccessLevel attribute of invalidated variables such that they are neither readable nor writable and the status of these variables shall be set to bad. Read and write service requests for invalidated variables shall return a failure.
The Device Definition can specify relationships between variables in a device. These relationships can impact the value of variables in the Information Model.
The FDI Server shall generate DataChange Notifications to any FDI Clients that are subscribing to Information Model elements that have changed.IEC 62769-3 pdf download.