Classifier & Owned Behavior

In SysML, a «block» is an element of classification.  In other words, it defines a type, or class, of objects.  The «block» defines system structure, but may also possess behavior.  The behavior owned by the «block» is often represented as a «stateMachine» or an «activity».

In the example, the «block», My Block, possesses two operations.  The first is typed by an «activity» called My Activity, and the second is typed by a «stateMachine» called My State Machine.  In general, operations which act as a function (i.e., inputs are transformed into outputs) are typed by an «activity» and operations which represent modes of operation of the system are typed by a «stateMachine».

SysML 1.4 added two new types of behavior owned by a «block»; one is classifier behavior, which is automatically executed each time an instance of a «block» is created.  There can be only one classifier behavior defined for a «block».  Classifier behavior is also called main behavior.  The second is called owned behavior, which consists of the set of all classifier behavior plus additional activities or state machines.  These behaviors may be displayed in their own compartments within the «block».

Note that an operation is not the same as a classifier or an owned behavior.Whereas classifier behavior of a «block» begins executing the moment an instance of the «block» is created, an operation is not executed until a request is made.As mentioned earlier, an operation may be typed by an activity.

Reference:

Friendenthal, S., Moore, A., & Steiner, R. (2012) A Practical Guide to SysML. Waltham, MA: Morgan Kaufmann. Pg. 148.