DiagramElements-Step/en

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Introduction[Bearbeiten]

A step is an action block which is placed into (instantiated in) an activity diagram. When a step is triggered (usually by receiving its required data at its input pins), an activity is triggered, which performs the action of block. Note that multiple activities can execute the same step if it is triggered multiple times and has been configured to operate in parallel and also that multiple different steps can be active at the same time. This happens when new data is coming in before the first activity is finished. If the parallelism is not limited, another activity will be triggered.

In workflow literature this term is used in the same tenor. In UML literature the terms "action", "activity" and "step" are unfortunately used inconsistently. The expecco documentation strictly separates between "action block" (= action definition), "step" (= placed block) and "activity" (= executed step). Please note that a block can be placed (instantiated) several times as a step and multiple activities could be actively executing the same step's action.

Types of Steps[Bearbeiten]

Every step has an associated action definition, which is executed whenever the step is triggered. The internals of a step depend on how the action is defined. It may be an elementary, compound or a builtin action. Elementary actions are defined by a piece of code written in a number of programming languages, compound actions are described by an activity diagram, and the action of a small number of builtin actions is hard wired into expecco. Builtin actions are for example, shell action steps and attachment steps, for which no particular action definition is required.

Regular Step[Bearbeiten]

Regular steps have an optional number of data and control inputs and an optional number of outputs. Each input and output is presented as a [[DiagramElements-Pin|pin|| in the action's schema definition. This schema definition can be seen as a template, which defines the outside picture of an action when placed as a step into an activity diagram.

Attachment Step[Bearbeiten]

Attachment steps do not have data inputs, but only provide a single output pin, at which the attachments contents is presented, when the step is triggered. Other than that, they behave like any other ordinary step (and in fact, an attachment could be easily simulated or reimplemented by an action which reads the file and passes the contents to its single output pin.

Triggering a Step[Bearbeiten]

A step in an activity diagram gets triggered when its required input values are available at its input pins. The details for triggering are described in the pin documentation, and are controlled by the number and type of input pins. However, the fast majority of actions are declared with a simple and intuitive "All connected pins must have a value" as triggering condition (the so called "And-Connected Trigger Condition"). Actions with no input pins usually have the "Autostart" attribute, which is described below.

Special Attributes of a Step[Bearbeiten]

Autostart[Bearbeiten]

Ignore Exception[Bearbeiten]

Skipped Execution[Bearbeiten]

Suppress Log[Bearbeiten]

See also: Block, Activity, DiagramElements-Pin, DiagramElements-Connection  

For other diagram elements see: Diagram Elements  

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