2.3 General FDT Architecture and Components

FDT is a specification of interfaces to facilitate the interaction between a device-specific application and a FDT Frame Application. This is shown below.

Figure 2-3 - The FDT Interfaces

As a runtime environment, a DTM needs a so-called FDT Frame Application. This Frame Application must provide the interfaces as defined in the FDT specification. Typically, the FDT-Frame Application comprises client applications that use DTMs, some kind of database for persistent storage of device/DTM data, and a communication link to the field devices. FDT-Frame Applications may be represented by applications like engineering tools for control systems (probably the complete control system) or standalone tools for device configuration. These applications are called ‘Frame Applications’. Throughout this document the terms ‘FDT-Container’ and ‘Frame Application’ are used as synonyms.

Client applications are seen to be single applications focusing on special aspects like configuration, observation, channel assignment etc. and using the functionality provided by the DTM who is the server.

The FDT Specification specifies COM interfaces (what the interfaces are), not the implementation (not the how of the implementation) of those interfaces. It specifies the behavior that the interfaces are expected to provide to client applications that use them. The FDT-Specification neither specifies the implementation of DTMs nor the implementation of Frame Application.

Included are descriptions of architectures and interfaces which seemed most appropriate for those architectures. Like all COM implementations, the architecture of FDT is a client-server model where DTMs are the Server components managed by the Frame Application.