Actions the Fundamental Behavioral Building Blocks

Actions are the behavioral atoms that are connected together to describe the behavior of an Activity, Sub-system, system or one of its parts. Effectively an Activity is made up of a set of Actions that work together to convert items (tokens) that are input into the Activity to items (tokens) that are output by the Activity. The first Action in a sequence will receive its inputs from one of the owning Activity's Input Parameter Nodes and the last Action in the sequence will place the output onto one of the Activity's Output Parameter Nodes. The Actions themselves have input and output devices called Pins - an Action will receive tokens on its Input Pins, perform its work and place the resulting tokens on its Output Pins.

Enterprise Architect has rich support for modeling Actions and their inputs and outputs, and various parts of the user interface can be used while working with these fundamental building blocks of behavior. There are a number of different types of Action available from the Toolbox.

An engineer can add an Action directly from the Toolbox, but it is more common to create Actions from existing Activities that have been defined in hierarchies, as described in the topic Creating Activity Hierarchies. To do this an Activity would be dragged NOT from the Toolbox but from the Browser window and dropped onto an open Activity diagram as an Invocation - this has the effect of creating an Action based on the Activity and placing it in the diagram.

The integrated Properties window makes it easy to work with Actions and their Pins. An engineer can specify a range of properties for the Action and its Pins, including the Pin Name, Type, Multiplicity, Direction and much more. The Properties window can be docked or made to float, and even dragged onto a different monitor; as elements are selected in the Browser window or a diagram the properties can be viewed, created or changed.

As a diagram is created, the elements that are added are automatically inserted into the Browser window, allowing an engineer to see a structural view of the Activity, Actions, Pins and other elements. Even if the diagram is not open the elements can be selected in the Browser window and edited directly in the Properties window.

A number of these properties will be displayed in the diagram in the Pin label, including name, type and multiplicity. The Multiplicity specifies both a lower bound and an upper bound. The lower bound specifies, for a given execution of the action, the allowable number of tokens that the pin can consume or create, and the upper bound specifies the maximum number of tokens that are consumed or created on that pin.

There is also a wide range of windows that can be useful when working with the Actions, including the Traceability Window,  which shows how elements are related regardless of where they are located in the repository; it also displays their structural features such as Pins and Parameters.