Definition: An interaction in which one entity regulates, modifies, or otherwise influences a continuant entity, i.e. pathway or interaction. Usage: Conceptually, physical entities are involved in interactions (or events) and the events are controlled or modified, not the physical entities themselves. For example, a kinase activating a protein is a frequent event in signaling pathways and is usually represented as an 'activation' arrow from the kinase to the substrate in signaling diagrams. This is an abstraction, called "Activity Flow" representation, that can be ambiguous without context. In BioPAX, this information should be captured as the kinase catalyzing (via an instance of the catalysis class) a Biochemical Reaction in which the substrate is phosphorylated. Subclasses of control define types specific to the biological process that is being controlled and should be used instead of the generic "control" class when applicable. A control can potentially have multiple controllers. This acts as a logical AND, i.e. both controllers are needed to regulate the controlled event. Alternatively multiple controllers can control the same event and this acts as a logical OR, i.e. any one of them is sufficient to regulate the controlled event. Using this structure it is possible to describe arbitrary control logic using BioPAX. Rationale: Control can be temporally non-atomic, for example a pathway can control another pathway in BioPAX. Synonyms: regulation, mediation Examples: A small molecule that inhibits a pathway by an unknown mechanism.
Source:http://www.biopax.org/release/biopax-level3.owl#Control