UML Modelling: Exercise Diagram

UML is a Unified modeling language. This UML language consists of quite a few distinct kinds of diagrams. In this short article we are speaking about about exercise diagram.


In its basic sort, an exercise diagram is a simple and intuitive clarification of what takes place in a get the job done stream, what steps can be done in parallel, and regardless of whether there are alternate paths by the work flow. These diagrams as outlined in the Unified Modeling Language [UML1.3] are derived from a selection of strategies to visually illustrate get the job done flows. Considerably of the foundation for the definition of the these diagram details is identified in [Martin & Odell].

We can use exercise diagrams to visualize the perform flow of a enterprise use case. An complete get the job done movement rationalization will have a fundamental circulation, and one or several option flows. This get the job done flow has a structure that we can describe textually, using informal if, if-then-else, or a do-until finally statements of different sorts. For a uncomplicated function circulation with a easy structure these kinds of textual definitions may perhaps be reasonably enough, but in the

case of additional composite constructions, these diagrams assist to illuminate and develop additional apparent what the work circulation is. Traditionally, these diagramming techniques have normally been utilized in the enterprise method modeling domain, but you can use it in the system modeling area also.


In June 2003, The Rational Edge launched a new posting collection by Donald Bell, IBM Global Products and services, known as UML principles. The reason of this series is to enable readers turn out to be familiar with the main diagrams that make a lot of the UML. Aspect I presented a general overview of these diagrams this thirty day period, we continue the series with a shut glimpse at the this diagram, counting this diagram’s entire UML v1.4 notation established.

The exercise diagram’s reason

The objective of the this diagram is to characterize the technological move of activities that are part of a greater action. In tasks in which use conditions are present, these diagrams can product a exact use circumstance at a additional detailed degree. Nonetheless, these diagrams can be made use of independently of use conditions for modeling a small business-stage perform, such as buying a live performance ticket or registering for a college course. Action diagrams can also be applied to model procedure-degree functions, these types of as how a ticket reservation facts mart populates a company revenue system’s information warehouse. Because it products procedural move, the action diagram focuses on the action collection of execution and the circumstances that activate or guard those people actions. This diagram is also targeted only on the activity’s inside steps and not on the actions that call the activity in their method circulation or that cause the action according to some celebration.

While UML sequence diagrams can depict the same information and facts as activity diagrams, I personally locate these diagrams exceptional for modeling company-degree features. This is because these diagrams reveal all possible sequence flows in an action, while a sequence diagram usually illustrates only one particular flow of an activity. In addition, small business administrators and business approach workforce seem to be to favor these diagrams extra than sequence diagrams — an exercise diagram is less “techie” in overall look, and consequently considerably less threatening to enterprise men and women. In addition, business supervisors are utilized to seeing stream diagrams, so the “appear” of an exercise diagram is acquainted.

When to Use: Action Diagrams

These diagrams must be employed in mix with other modeling strategies these types of as interaction diagrams and condition diagrams. The essential motivation to use these diagrams is to model the get the job done movement guiding the procedure being planned.

Action Diagrams are also beneficial for:

  1. Analyzing a use situation by describing what actions require developing and when they should occur.
  2. Describing a complex sequential algorithm.
  3. Modeling programs with parallel processes.

Even so, activity diagrams really should not acquire the place of conversation diagrams and condition diagrams. these diagrams do not give element about how objects behave or how objects collaborate.


Exercise diagrams are graphical demonstrations of function flows of step intelligent routines and steps with maintain for option, iteration and concurrency. In the Unified Modeling Language, these diagrams can be utilized to portray the enterprise and operational move-by-move function flows of mechanisms in a method. In this diagram it illustrates the in normal move of manage.

Activity diagrams convey the operate flow efficiency of a process. These diagrams are parallel to point out diagrams simply because functions are the condition of doing one thing. The diagrams describe the state of functions by presenting the sequence of routines executed. These diagrams can ensure activities that are conditional or parallel.


Exercise diagrams are built from a limited quantity of styles, linked with arrows. The most considerable condition varieties:

  • Rounded Rectangles correspond to Routines
  • Diamonds symbolize Choices
  • Bars symbolize the start (split) or conclude (be a part of) of concurrent actions
  • Black circle stands for the commence (original point out) of the function move
  • Encircled black circle signifies the finish (ultimate state).
  • Arrows run from the commence towards the end and characterize the buy in which pursuits occur.

As a result, all these designs can be considered as a type of flowchart. Usual flowchart methods are limited of constructs for expressing concurrency. Nonetheless, the join and split symbols in this diagrams only identify this for easy cases. The sense of the representation is not understandable when they are randomly mixed with selections or iterations.

Description, indicating, and sequence of the standard notations:

  • Preliminary node: The loaded in circle is the starting up issue of the diagram. An initial node is just not essential although it does make it greatly a lot easier to browse the diagram.
  • Activity last node: The crammed circle with a border is the ending level. An action diagram can have zero or a lot more action ultimate nodes.
  • Action: The rounded rectangles represent routines that arise. An exercise may possibly be bodily, these as Examine Forms, or electronic, these types of as Show Make Pupil Display.
  • Circulation/edge or arrows on the diagram: Even though there is a refined big difference between flows and edges I have under no circumstances noticed a simple function for the distinction despite the fact that I have no question a single exists. I will use the term stream.
  • Fork: There is a black bar with one particular flow going into it and quite a few leaving it. This denotes the beginning of parallel activity.
  • Join: There is a black bar with many flows entering it and a single leaving it. All flows heading into the sign up for will have to reach it just before processing may possibly continue. This denotes the conclusion of parallel processing.
  • Issue: In the diagram, there is a textual content this kind of as [Incorrect Form] on a circulation, defining a guard which need to appraise to legitimate in get to traverse the node.
  • Determination: There is a diamond with one particular flow moving into and numerous leaving. The flows leaving contain circumstances while some modelers will not reveal the conditions if it is apparent.
  • Merge: There is a diamond condition with quite a few flows entering and one leaving. The implication is that just one or a lot more incoming flows ought to achieve this level until processing continues, centered on any guards on the outgoing circulation.
  • Partition: This is arranged into a few partitions, also known as swimlanes, indicating who/what is doing the functions (Applicant, Registrar, or Technique).
  • Sub-exercise indicator: The rake in the base corner of an exercise, these types of as in the Use to College exercise, suggests that the activity is explained by a much more finely in depth action diagram.
  • Flow ultimate: If there is the circle with the X by it termed stream ultimate. This suggests that the process stops at this place.

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