Linked composites

Linked composites also provide some useful features, but a greater understanding of how linked composites work is essential for you to fully take advantage of these features. With linked composites, you develop and maintain the control logic once, and that structural information can be used in several different control modules. The structural information is always maintained in the library, while the parameter information is stored within the control module itself.

By storing the parameter information in the control module, you can adjust the values of the composite for each control module that references it. When a library composite is placed on a diagram as a linked composite, all the parameter information associated with that library composite is copied, with default values, to the control module. To modify these values for a specific control module, double-click the composite when the composite is selected from within the control module's diagram. You can then adjust the default values to the values you want to use. The control module stores all the parameter values that were changed from the library default values.

If, at a later time, you modify the default value in the library for a parameter, any control module that has not had that parameter modified also receives the updated parameter value. For example, if you modify the default value for parameter ABC, any module for which that default value has not been set receives the new value as the default. Modules in which parameter ABC was modified are unaffected by the parameter change in the library.

You can also change a default parameter value in a single instance of the composite template by disconnecting (de-linking) the parameter from the template. Open the instance of the composite, right-click the parameter, and then select Properties. Deselect the Use Default Value from Composite Template option. The composite is still linked to the template, but this parameter's default value can now be changed for this instance of the module.

The structural information of a linked composite is stored in the library. Changing any structural information on the library composite automatically modifies all control modules that reference the library composite. There are three ways to edit the structural information of a library composite:

• From within the DeltaV Explorer, right-click the composite in the Library, and then select Edit. This launches a Control Studio window.

• From within Control Studio, click the Main button, and then click Open. Click Objects of Type: Composite Templates. Then select the desired library composite by name and click OK.

• While editing a control module from within Control Studio, right-click a linked composite, and then select Edit Object. This launches a second Control Studio window with the composite loaded and ready for editing.

If you want to be able to change the original composite block definition and have that change propagate to all of the other composites you create from the block, use a linked composite. This way, you can fix or edit a composite in one place and all of the other linked blocks are changed automatically. When you link a composite block, it gets updated if you modify the original block or the composite template it was created from. Linked data is stored in the source block; the block you create from the original stores the location of the source block and displays a representation of the original block.