The Unified Modeling Language User Guide

1
The Unified Modeling Language User Guide

• Chapter 15
• Interactions

2
Chapter 15 Topics

• Introduction
• Terms and Concepts
• Common Modeling Techniques

3
Introduction

• Objects communicate with each other by sending
  messages. Sending a message is another name for
  a member function call.
• Some C examples of member function calls ...
• objectName.messageName( )
• objectPointer-gtmessageName( )
• (objectPointer).messageName( )
• An interaction is a set of messages exchanged
  among a set of objects in order to accomplish a
  specific goal.

4
Introduction

• Interactions model the dynamic aspects of a
  system by showing the message traffic between a
  group of objects.
• Showing the time-ordering of the message traffic
  is a central ingredient of interactions.
• Graphically, a message is represented as a
  directed line that is labeled.

5
Introduction
6
Terms and Concepts

• Context
• Interactions appear whenever an object is linked
  to another object.
• Links
• A link is an instance of an association.
• Links must exist for interactions to occur.
• The multiplicity on both ends of a link is 1,
  since it is an instance of an association.

7
Links and Associations
8
Terms and Concepts

• Messages
• A message is the vehicle by which communication
  between objects is achieved.
• A call is the most common type of message.
• The return of data as a result of a function call
  is also considered a message.
• A message may result in a change of state for the
  receiver of the message.
• The receipt of a message is considered an
  instance of an event.

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Sequence Diagram
10
Terms and Concepts

• Sequencing
• A sequence of messages is rooted in some process,
  thread or hardware event.
• A sequence will continue as long as the process
  that started it lives.
• Messages in sequence are ordered by time.

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Terms and Concepts

• Creation, Modification, and Destruction
• There are three predefined stereotypes that can
  adorn an interaction for purposes of showing the
  life span of a link or, more commonly, the life
  span of an object participating in the link.
• ltltnewgtgt -- interaction results in the creation
  of a new object.
• ltltdestroyedgtgt -- interaction results in the
  destruction of an existing object.
• ltlttransientgtgt -- link will be destroyed before
  the completion of the interaction.

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Terms and Concepts

• Representation
• Interactions are be modeled using interaction
  diagrams.
• There are two types of interaction diagrams.
• Sequence diagrams emphasize the time ordering of
  the interactions.
• Collaboration diagrams emphasize the structural
  organization of the objects participating in
  interactions.
• Both types convey the same information, but with
  a different emphasis.
• The type of diagram used is largely a matter of
  personnel preference.

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Common Modeling Techniques

• It is impossible to model all possible
  interactions within a system.
• Only model those interactions that are
  interesting or shed light on important aspects of
  the system.
• A system of even modest complexity may require
  several interaction diagrams.
• It does not matter whether you use interaction or
  collaboration diagrams to model interactions.

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Sequence / Collaboration Diagram Comparison
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Sequence / Collaboration Diagram Comparison