Operational Views (OV) [Logical Views]

OV-6b Operational State Transition Description

The Operational State Transition Description is a graphical method of describing how an Operational Node or activity responds to various events by changing its state. The diagram represents the sets of events to which the Architecture will respond (by taking an action to move to a new state) as a function of its current state. Each transition specifies an event and an action.

Background:

An OV-6b can be used to describe the detailed sequencing of activities or work flow in the business process. The OV-6b is particularly useful for describing critical sequencing of behaviours and timing of operational activities that cannot be adequately described in the Activity Model (OV-5).

The OV-6b relates events and states. A change of state is called a transition. Actions may be associated with a given state or with the transition between states in response to stimuli (eg triggers and events).

Usage:

Data objects:

The data in an OV-6b can include:

Representation:

Detailed Product Description:

The Operational State Transition Description (OV-6b) reflects the fact that the explicit sequencing of activities in response to external and internal events is not fully expressed in OV-5. Alternatively, OV-6b can be used to reflect the explicit sequencing of actions internal to a single Operational Activity or the sequencing of operational activities with respect to a specific operational node.

OV-6b is based on the statechart diagram. A state machine is defined as “a specification that describes all possible behaviours of some dynamic model element. Behaviour is modelled as a traversal of a graph of state Nodes interconnected by one or more joined transition arcs that are triggered by the dispatching of a series of event instances. During this traversal, the state machine executes a series of actions associated with various elements of the state machine.”

State chart diagrams can be unambiguously converted to structured textual rules that specify timing aspects of operational events and the responses to these events, with no loss of meaning. However, the graphical form of the state diagrams can often allow quick analysis of the completeness of the rule set, and detection of dead ends or missing conditions. These errors, if not detected early during the operational analysis phase, can often lead to serious behavioural errors in fielded systems or to expensive correction efforts.

The Figure below provides a template for a simple OV-6b. The black dot and incoming arrow point to initial states (usually one per diagram), while terminal states are identified by an outgoing arrow pointing to a black dot with a circle around it. States are indicated by rounded corner box icons and labelled by name or number and, optionally, any actions associated with that state. Transitions between states are indicated by one-way arrows labelled with an event/action notation that indicates an event-action pair, and which semantically translates to: when an event occurs, the corresponding action is executed. This notation indicates the event that causes the transition and the ensuing action (if any) associated with the transition.


State transitions

The following figure provides an example View Product.


Example OV-6b

States in an OV-6b View Product may be nested. This enables quite complex models to be created to represent operational behaviour.

Page version 1.1, dated 4th April 2007

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