Smith’s Aerospace © P. Bailey & K. Vander Linden, 2005

Procedural Activity

Patrick BaileyKeith Vander LindenCalvin College

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Smith’s Aerospace © P. Bailey & K. Vander Linden, 2006

Procedural Activity● Systems display procedural activity:

– Business work-flow– Data flow– Task behavior– Concurrent processes

● Potential modeling solutions:– Flow charts– State diagrams– Activity diagrams

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Smith’s Aerospace © P. Bailey & K. Vander Linden, 2006

Activity Diagrams● Activity diagrams

model activities as:– Actions– TransitionsWith additional features

for decisions, forks, joins, etc.

● They use many of the same elements provided for state diagrams.

Example adapted from Fowler, 2004

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Outline● History● Activity Diagrams● Examples● Using Activity Diagrams

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Smith’s Aerospace © P. Bailey & K. Vander Linden, 2006

● 1962● Extended state

machines with token flow to represent concurrency

● UML 2.0 activity diagrams use token flow and a similar structure.

Carl Adam Petri (1926- )Petri-Nets

Images from www.informatik.uni-hamburg.de, August, 2005

Petri Net for 4 dining philosophers.

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Smith’s Aerospace © P. Bailey & K. Vander Linden, 2006

Actions● Actions represent an

encapsulated unit of activity.● They must have at least one

incoming and one outgoing transition.

● Actions can be implemented as:– Class methods– Code fragments– Sub-activities

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Action Decomposition Actions can be

decomposed.

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Signals Actions can

respond to and produce external signals:– Time signals– Other signals

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Smith’s Aerospace © P. Bailey & K. Vander Linden, 2006

Transitions● Transitions (aka. flows, edges)

are like state diagram transitions except that they are not event-driven by default.

● Behavior:– They transition in when all

incoming transitions join.– They transition out when their

action is complete.● Use connecters as a shorthand.

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Smith’s Aerospace © P. Bailey & K. Vander Linden, 2006

Data Flow● Transitions can

carry parameter objects.

● You can use pins to specify them.

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Smith’s Aerospace © P. Bailey & K. Vander Linden, 2006

Connectors Connectors come in

various forms:– Decision connectors

– Junction connectorsRegular Delivery

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Example adapted from Fowler, 2004

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Smith’s Aerospace © P. Bailey & K. Vander Linden, 2006

Synchronization Bars● Concurrency is modeled with

token flow in activity diagrams.● Tokens are:

– Created at initial nodes– Passed from action to action

during activities– Spawned at fork nodes– Joined a join nodes– Consumed at final nodes

● The token flow must be “balanced”.

Example adapted from Fowler, 2004

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Termination States Termination states represent either

local or global termination, depending upon context.− Activity Final

− Flow Final

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Smith’s Aerospace © P. Bailey & K. Vander Linden, 2006

Partitions● Activity

diagrams don’t naturally specify agency.

● Use partitions (aka. swim lanes) to do this.

Example adapted from Fowler, 2004

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Example: Parallel Algorithm

Example from Douglass, Real Time UML, 2004

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Example: HCI

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Smith’s Aerospace © P. Bailey & K. Vander Linden, 2006

Using Activity Diagrams● Activity diagrams can represent:

– Concurrency– Inter-object procedural sequences

● They can be used to specify process for:– State activities (entry, exit, transition, do)– Use cases– Classes

● Real-time modeling uses them primarily for concurrent algorithm specification.