Object-Oriented Design Activity Diagrams Sharif University of - - PowerPoint PPT Presentation

Department of Computer Engineering

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Object-Oriented Design

Activity Diagrams

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Analysis Workflow: Analyze a Use Case

• The analysis workflow consists of the following activities:
• Architectural analysis
• Analyze a use case
• Outputs:
• analysis classes
• use case realizations
• Analyze a class
• Analyze a package

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Activity Diagrams

• Activity diagrams are OO flowcharts:
• used for modeling all types of processes;
• can be attached to any modeling element to capture its behavior;
• a good activity diagram communicates one specific aspect of a

system's behavior;

• in UML 2, activity diagrams have Petri Net semantics.

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Activities

• Activities are networks of nodes connected by edges.
• Categories of nodes:
• action nodes - atomic units of work within the activity;
• control nodes - control the flow through the activity;
• bject nodes - represent objects used in the activity.
• Categories of edges:
• control flows - represent the flow of control though the activity;
• bject flows - represent the flow of objects through the activity.
• Activities can have preconditions and postconditions.

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Activities: Example

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Activity Diagrams: Use Case Modeling

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Activities: Tokens

• Tokens flow around the network and can represent:
• the flow of control;
• an object;
• some data.
• Tokens move from a source node to a target node across an edge depending on:
• source node postconditions;
• edge guard conditions;
• target preconditions.

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Activity Partitions

• Activity partitions - a high-level grouping of related actions.
• Partitions form a hierarchy rooted in a dimension.

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Action Nodes

• Execute when there is a token simultaneously on each of their input edges AND

their preconditions are satisfied.

• After execution, action nodes offer tokens simultaneously on all output edges

whose postconditions are satisfied:

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Action Nodes: Types

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Action Nodes: Call

• Call action node:
• call an activity - use the rake symbol;
• call a behavior;
• call an operation.

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Action Nodes: Accept Time Event

• Accept time event action node - executes when its time expression

is true:

• an event in time (e.g., end of business year);
• a point in time (e.g., on 11/03/1960);
• a duration (e.g., wait 10 seconds).

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Control Nodes

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Control Nodes: Decision and Merge

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Control Nodes: Fork and Join

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Object Nodes

• Object nodes represent instances of a classifier.
• Input and output edges are object flows - represent the movement of objects.
• Object node output edges compete for each output token.

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Object Nodes: Buffer Semantics

• Object nodes act as buffers:
• {upperBound= n};
• {ordering= FIFO} XOR {ordering= LIFO};
• {ordering= FIFO} is the default;
• may have a «selection».
• Object nodes can represent objects in a particular state.

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Object Nodes: Activity Parameters

• Activity parameters are object nodes input to or output from an activity:
• drawn overlapping the activity frame;
• input parameters have one or more output edges into the activity;
• utput parameters have one or more input edges out of the activity.

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Pins

• A Pin is an object node that represents one input to or output from an action or

activity.

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Connectors

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Interruptible Activity Regions

• interrupted when a token traverses an interrupting edge.
• all flows in the region are aborted when it is interrupted.
• interrupting edges are drawn as a zigzag arrow or as a normal arrow with a

zigzag icon above it.

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Exception Handling

• Exception pins:
• output an exception object from an action;
• are indicated with an equilateral triangle.
• Protected nodes:
• have an interrupting edge leading to an exception handler;
• abort when an exception of the right type is raised, and flow passes to the exception

handler node.

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Expansion Nodes

• Represent a collection of objects flowing into or out of an expansion region.
• The region is executed once per input element.
• Constraints:
• the type of the output collection must match the type of the input collection;
• the type of object held in the input and output collections must be the same.
• Modes:
• Iterative - process each element of the input collection sequentially;
• Parallel - process each element of the input collection in parallel;
• Stream - process each element of the input collection as it arrives at the node;
• there is no default mode.

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Expansion Nodes: Example

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Sending Signals and Accepting Events

• Signals:
• information that is passed asynchronously between objects;
• class stereotyped «signal»;
• the information is held in the attributes.

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Sending Signals and Accepting Events: Action Nodes

• Send Signal action node:
• starts when there is a token on all input pins;
• executes - a signal object is constructed and sent;
• then ends and offers control tokens on its output edges.
• Accept Event action node:
• started by an incoming control edge or if no incoming edge, when its
• wning activity starts;
• waits for an event of the specified type:
• utputs a token that describes the event;
• continues to accept events while the owning activity executes;
• for a signal event, the output token is a signal.

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Sending Signals and Accepting Events: Examples

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Streaming

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Advanced Object Flows

• input and output effects show the effects an action has on its input

and output objects:

• write the effect in braces close to the pin;
• selection - a condition on an object flow that causes it to accept
• nly those objects that satisfy the condition:
• put the selection condition in a note stereotyped «selection» attached to

the object flow;

• transformation - transforms objects in an object flow to a different

type:

• put the transformation expression in a note stereotyped «transformation»

attached to the object flow.

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Input and Output Effects

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Multicast and Multireceive

• Multicast sends an object to many receivers:
• stereotype the object flow «multicast».
• Multireceive receives objects from many senders:
• stereotype the object flow «multireceive».

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Parameter Sets

• Parameter sets allow an action to have alternative sets of input and output pins:
• input parameter sets contain input pins;
• utput parameter sets contain output pins;
• nly one input parameter set and one output parameter set may be used per

execution of the action.

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Central Buffer Nodes

• Central buffer node - object nodes that are used specifically as

buffers:

• stereotype the object node «centralBuffer».

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Interaction Overview Diagrams

• Interaction overview diagrams show flow between interactions

and interaction occurrences

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Reference

• Arlow, J., Neustadt, I., UML 2 and the Unified Process: Practical Object-

Oriented Analysis and Design, 2nd Ed. Addison-Wesley, 2005.