2.10 Abstract FDT Object Model

This is the view on the device itself to integrate the I/O structure for Frame Application tasks like channel assignment and controller configuration. An object model of DTMs, BTMs and FDTChannels serves the access to this information. Only DTM, BTM, Channel and presentation objects are implemented as COM objects. Information about the Frame Application, project or DCS channels is provided using XML documents. Also information about functionality and properties of the DTM, BTM and channel objects is available via XML documents and exchanged via COM interfaces of these objects.

Object	Description
FrameApplication	The FrameApplication is a logical object to represent an environment like an engineering system or a standalone tool. It controls the lifetime of DTM-instances within the project. A Frame Application can handle several projects
Project	The Project is a logical object to describe the management and controls at least the lifetime of device-instances within a Frame Application. That means at least the management of instance data sets within a database or file system. The Project belongs to the Frame Application.
DTM	Each device is represented by a DTM object. This object is the starting point for navigation to the finer parts of the device like modules and channels. A device can be subdivided into modules and sub modules. A module is either a hardware module or a software module. Hardware modules are plugged into physical slots of the device. For example, an I/O module can be plugged into a Remote I/O device. A module can also be a software module. Software modules represent static or configurable substructures of a device like a closed loop module. These SW modules in general are device specific and can not be moved between devices. A DTM may represent different types of devices, e.g. field devices, communication devices and gateway devices. A Device-DTM represents a 'normal' field device that uses a Communication-Channel to communicate with the related field device A Communication-DTM represents a communication device that provides communication capabilities via Communication-Channels (in sense of FDT) but does not needs any communication capabilities of a parent DTM A Gateway-DTM is a Communication-DTM that provides communication capabilities via Communication-Channels (in sense of FDT) and requires communication capabilities of a parent DTM
BTM	A BTM is used to represent flexible software objects, like function blocks. These software blocks are more flexible than Software modules, for instance they may be moved between devices. Also a protocol may require modeling of device structures as blocks.
FdtChannel	FdtChannel-Object could behave in 2 ways: As a ‘Communication-Channel’ and a ‘Process-Channel’. Communication-Channel is an object that provides access to communication infrastructure. It is used by Device-DTM or Gateway-DTM as a service provider for communication. Process-Channel represents a single process value, its optional state information, and its assigned ranges and alarms. A channel either belongs to a device or a module DTM. An FdtChannel-Object could implement both behaviors.
Presentation	Presentation objects represent a (visual) user interface. A presentation object can be an ActiveX control provides by a DTM or it can be encapsulated in case of monolithic DTMs The Presentation object belongs to the DTM
DcsChannel	The DcsChannel is a logical object representing a part of a DCS function. To make the cyclic I/O data available within a Frame Application there must be an association between the I/O function blocks and the process values of a device. The inputs and outputs of I/O function blocks are represented by DcsChannels, the process value by an FdtChannel and the association is called channel assignment. A DcsChannel belongs to the Frame Application.

All the associations shown in the object model above are listed in the table below.

Name	Description
Devices	Within a project it is important to known all field devices. This association enumerates all field devices in the project. It also forces DTMs with private instance database to collaborate with the project for creation and removal of field devices. The removal of the project forces all DTM instances to be removed. A DTM instance (field device) cannot be part of more than one project.
Channels	A channel is part of a DTM. The creation of channel instances is controlled by a DTM on the next higher level. This can be a DTM for a device or a module
Show	The instances of presentation objects are associated to the instance of their DTM business object by this relationship. This association belongs to the type of application.
Instantiate	This association shows for ActiveX controls that the presentation objects of a DTM are at least instantiated and embedded by the Frame Application.
Channel- Assignment	To make the cyclic I/O data available within a Frame Application there must be an association between the I/O function blocks and the process values of a device. The I/O function blocks are represented by a DcsChannel, the process value by an FdtChannel and the association is called channel assignment The Frame Application (project) is responsible for handling this association.
LinkedDevice	The topology of field devices is shown with this association. Within the topology tree a channel object is the parent node for a device. The association shows the connection from a channel to a device. Linked devices are available via GetChildNodes() The Frame Application (project) is responsible for handling this association.
LinkedChannel	The topology of field devices is shown with this association. Within the topology tree a DTM object as proxy for a device is the child node of a channel. The association shows the connection from a device to a channel. The channel is available via GetParentNodes() The Frame Application (project) is responsible for handling this association.

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Last updated 2015-02-05 15:17
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