The DEAT Business Rule Pattern Language

Russell R. Hurlbut, Ph.D.

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Rule Pattern 17: State Transitions

Problem Describing a Restriction on the Transition of One State to Another for an Entity

Business processes rely on certain conditions being fulfilled before an entity may move from one state to another state. Those conditions frequently include specified sequences of states that must progress in a prescribed order.

Solution

Valid state transition may be defined by means of ordered transitions that are characterized by transition types such as progressive, reinitiating, and cycle. Representation may take several forms, including a state transition matrix or state machine model. The manner used for parameter driven business rules is a regular expression grammar. This key aspect of this business rule type is the specification of the primary transition paths in order to describe the overall nature of the state transitions rather than an exhaustive definition of all permutations. Accordingly, it may be used as a starting point in defining a complete state transition matrix. This business rule pattern captures the distinctive elements of an entity's life cycle in a manner compatible with the product of the event-sate cluster analysis described in chapter seven.

Example Employment Status

The first status for an employee must always be active. Any other status may follow. A terminated status is a terminal status, but unlike deceased it can lead to a cycle of active status through a rehire event. Intervening status types include laid off, leave of absence, and suspended. Any of these must reinitialize to an active status or conclude a cycle with a terminated status.
Employment Status Parameters
Transition type Transitions
reinitializing active.[leave of absence | suspended | laid off]
cycle active.[leave of absence | suspended | laid off].terminated
progressive active.[retired | deceased]

UML Representation and Related Patterns

. The State Transitions business rule pattern maps to the Transition model element.

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