(transforming or enabling) link with a control modifier—the letter e (for event) or c (for condition), which adds semantics of a control element. The letter e signifies an event for triggering the linked process, while the letter c signifies a condition for execution of the linked process, or connection of two processes denoting invocation, or exception. Procedural link uniqueness OPM principle A process needs to transform at least one object. Hence, a process shall be connected via a transforming link to at least one object or object state. At any particular extent of abstraction, an object or any one of its states shall have exactly one role as a model element with respect to a process to which it links: the object may be a transformee or an enabler. Additionally, it can be a trigger for an event (if it has the control modifier e), or a conditioning object (if it has the control modifier c), or both. State-specified procedural links A state-specified procedural link is a detailed version of its procedural link counterpart in that rather than connecting a process to an object, it connects a process to a specific state of that object. Transforming links The three kinds of transforming links are: Consumption link: Graphically, an arrow with a closed arrowhead pointing from the consumee to the consuming process defines the consumption link. By assumption, the consumed object disappears as soon as the process begins execution. The syntax of a consumption link OPL sentence is: Processing consumes Consumee. Effect link: A transforming link specifying that the linked process affects the linked object, which is the affectee, i.e., the process causes some unspecified change in the state of the affectee. Graphically, a bidirectional arrow with two closed arrowheads, one pointing in each direction between the affecting process and the affected object, shall define the effect link. The syntax of an effect link OPL sentence is: Processing affects Affectee. Result link: Graphically, an arrow with a closed arrowhead pointing from the creating process to the resultee shall define a result link. The syntax of a result link OPL sentence is: Processing yields Resultee. Enabling links An enabling link is a procedural link specifying an enabler for a process—an object that must be present for that process to occur, but the existence and state of that object after the process is complete are the same as just before the process began.