To know more about the Reaction Feature...

To cope with the rules limitations and to create more associative and reactive design, the reaction feature is created.

A reaction is similar to a rule in the fact that:

	It is stored in the model
	It reacts to changes and triggers modifications
	It references also other objects and parameters in the document and supports replace mechanism
	It can be used for the definition of power copies and user defined features

But

	It can react to a larger amount of changes
	It can drive very complex modifications

A reaction is a feature that reacts to events and that triggers an action

The source can be:

	A selected feature (or a list)
	A parameter (result of a test)

Events can be:

	General events on objects (creation, destruction, update, attribute changes) and parameters (value change)
	Specific events such as a power copy or a UDF instantiation/update

	Reaction features provide a better control over when the rule is triggered.
	Reactions enable the user to perform more complex actions. As you better control when the action is triggered, and as you're not limited with the update mechanism, you can use all the power of any Visual Basic API (in CATIA but also in other automation applications...), and Visual basic macro with arguments can be called from an action.
	Reactions can be written to customize the update mechanism (to optimize user features for example).
	Reactions can react to user actions (instantiation of a user defined feature), insertion of a component in an assembly, modification of a parameter...
	Reactions can be combined with UDFs.