Business analysts use state modelling to describe and analyze the various potential states of an entity within a system. This includes how that entity changes from one state to another, and what can happen to the entity when it is in each state.
An entity is an object within a system which can be used in several processes. Every entity’s life cycle has a beginning and an end.
In a state or state transition model, a state is a formal depiction of a status. It is used when it is necessary to have an accurate and shared understanding of an entity that has complicated behaviour and rules.
A state model describes the following:
- A set of potential states for an entity.
- The order of states that the entity can be in.
- How an entity changes from one state to another.
- The events and conditions that cause the entity to change states.
- The actions that can or must be taken by the entity in each state as it goes through its life cycle.
While a process model can show all of the entities that are used in or affected by that process, a state model shows an integral view, i.e. what happens to one entity across all the processes that affect or use it.
State models have some components which include the following:
1 State: An entity has a limited number of states during its life cycle, although it can be in more than one state at any point in time. Each state is described with a name and the activities that could be performed while in that state.
There may be rules about which activities must or can be performed and which events it can respond to or prompt. A complex state can be broken down into sub-states.
2 State transition: how the entity transitions from one state to another could be determined by the steps of a process, business rules, or information content.
The order of states of an entity are not always linear; an entity could leap over several states or return to a previous state, even more than once.
A transition may be dependent on a specific event or a condition being met or it may also be automatic and is prompted by the realization of the required activities while in the previous state. It may also be recurrent, leaving one state and returning back to that same state.
A transition is described in terms of the event that causes the transition, conditions which decide whether or not the entity must respond to that event, and actions that occur in connection with that event.
3 State diagram: A state diagram shows the life cycle of one entity, beginning when the entity first comes into actuality and moving through all of the different states that the entity may go through until it is disposed of.
A state on a state diagram is shown as a rectangle with rounded corners, there may be any number of states and a state may be broken down into sub-states.
The transition from one state to another state is shown with a one-directional arrow pointing from the opening state to the final state. Tt can be labelled with the name of the event that causes the entity’s state to change from one state to another, and the conditions and actions.
The beginning and end of the entity’s life cycle are shown with special symbols for both the initial state, which shows that the entity has come into reality, and the final state, which shows that the entity is disposed of and the life cycle is complete.
4 State tables: A state table is a two-dimensional matrix which shows the different states and the transitions between them. It can be used during the elicitation and analysis activities either as an substitute, a predecessor, or an accompaniment to a state diagram.
It is an easy way to get started on a state model by obtaining the state names and event names from the domain subject matter experts. Each row shows an initial state, the transition, and the final state.
If one state could respond to numerous transitions, there will be a different row for each transition. A state that appears as an final state in one row could be an initial state in another row.
State models have both their strengths and limitations, which include the following:
Strengths
• It identifies the business rules and information characteristics that apply to the entity being modelled.
• It identifies and defines the activities that apply to the entity at different states of the entity.
• It is a more successful documentation and communication tool than text, especially if the entity is being described with more than a few states, transitions, and conditions ruling those transitions.
Limitations
• Ii is generally used only to understand and communicate information entities that are complex; simple entities can be understood without the time and effort needed to build a state model.
• Building a state model may seem simple in the beginning, but getting the domain SMEs to agree about the details needed to create the model can be difficult and time-consuming.
• The business analyst has to be highly skilled and experienced to build a state diagram.