Analyzing Interactions › Analyzing Entity Type Life-Cycles › Entity States

Entity States

The entity type life-cycle consists of a series of entity states, that have been defined as subtypes in the life-cycle partitioning.

An entity can exist in one of four states:

• Creation or starting state
  • The creation state is the initial state of an entity after the business becomes interested in it.
  • An entity type have multiple possible creation states in its life-cycle. This is the point at which the enterprise first records information about entities of importance to the business as it becomes aware of them.
  • Each entity type must have at least one creation state in its life-cycle, but many have more than one.
• Termination or ending state
  • The enterprise lose interest in information about an entity. It can then choose to stop keeping that information readily available, or available at all, and set the information aside in some way. The termination state is this final state in the life of an entity.
  • Each entity type have at least one termination state in its life-cycle, but have more than one.
  • An entity in a termination state, by definition, cannot be changed to another state, although it can be referenced (read).
  • Often, the entity still be of interest to the business when it is in a termination state, in which case the termination state is said to be indefinite, and the entity is not deleted. For example, retired employees remain of interest until some fixed period after death.
  • If the entity is truly no longer of interest to the business, it is deleted. In this case, the termination state is said to be definite.
• Null state
  • Entities exist before the enterprise have information about them available. This unavailability of information is known as a null state.
  • It is convenient to visualize the creation of an entity as involving a transition from a null state to a creation state. For example, the Add Customer process change the state of a customer entity from the null state to a creation state.
  • The null state also be a definite termination state that results from a deletion. The null state never explicitly appears as an entity state subtype in a life-cycle partitioning of an entity type.
• One or more intermediate states that are of interest to the business
  • Any state that is not a creation, termination, or null is named an intermediate state.
  • Intermediate states are represented only if they are of interest to the business, and affect the way that executions of business activities interact with entities. The intermediate states come about because the enterprise adds to, or changes, information that is recorded about an entity or its relationships with other entities. At some point, the differences from the previously recorded information become so significant that they affect the way that business processes with the entity, or even require that different processes may or may not deal with the entity. At these points, the business recognizes that an entity must change its state.
• Until an entity reaches a termination state, it move from state to state without restriction. An entity return to a previous state or skip a state, as long as the life-cycle of its entity type supports such behavior. So, although an entity pass from its creation state to its termination state, it need not pass through all the intermediate states sequentially. Some entities take a complex and repetitive path.

The lives of different entities of the same type can vary greatly from one another, based on the complexity of their entity type life-cycle. While every entity type has a life-cycle, many are so simple that they do not require explicit definition.

The simplest entity type life-cycle has only one explicit state indicating its existence. When an entity of this type is created, it moves from the null state to the creation state Exists. When it is deleted, it returns to the null state as its termination state. A life-cycle partitioning never explicitly partitions entity types with such simple life-cycles.

The following illustration shows an entity type with a simple life-cycle.

A customer is either active, suspended, or does not exist. Its creation state is simply Active, and its termination state is Suspended.

Customer does not need a life-cycle partitioning; nor is it necessary to develop an Entity Life-cycle Diagram for such a trivial case.

For a given life-cycle partitioning, every entity is in only one state at a given point in time.

Every entity type has at least one creation and one termination state. Since the termination state is null, it is not specified explicitly.