Interactions in UML

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Interactions in UML-OOAD Lecture Notes Pdf
Interactions 
  • Objects and Roles 
  • Links 
  • Messages 
  • Sequencing 
  • Creation, Modification and Destruction 
  • Common Modeling Techniques
Objects and Roles 
  • Objects are either concrete things or prototypical things 
  • Concrete thing represents something in real world while prototypical thing stands for any object of a given class 
  • In interactions, the interactors are usually prototypical things that play particular roles 
Example: 
  • When we say "Dhawan is the man of the match", we are referring to a particular instance of the player class. This is an example for concrete things 
  • When we say "a player is selected on merit", we are referring to any instance of player class. This is an example for prototypical things
Link
Link is 
  • Semantic connection among objects 
  • Instance of an association, i.e., the association between instances of two classes represents a link 
Link specifies a path to send and receive messages between two objects 
  • Association: Object is visible by association 
  • Self: Object is visible because it is the dispatcher of the operation 
  • Global: Object is visible because it is in enclosing scope 
  • Local: Object is visible because it is in a local scope 
  • Parameter: Object is visible because it is a parameter
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Messages 
Indicates an action to be done (requested by the sender to the receiver) 
Different types of messages are 
  • Call: Invokes an operation on an object; an object may send a message to itself, resulting in the local invocation of an operation 
  • Return: Returns a value to the caller 
  • Send: Sends a signal to an object 
  • Create: Creates an object 
  • Destroy: Destroys an object. An object may destroy itself
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Sequencing
  • A sequence is a stream of messages exchanged between objects 
  • Sequence must have a beginning Messages are ordered in sequence by time and are visualized by prefixing the message with a sequence number with a colon separator 
  • Flow of control are two types: 
A procedural or nested flow of control is rendered by using a filled solid arrowhead 
A flat flow of control is rendered by using a stick arrowhead
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Creation, Modification and Destruction 
Enabled by adding the following constraints to the element
  • New - This instance or link is created while the closing interaction is executed 
  • Destroyed - This situation or link is destroyed before the closing interaction is  completed
  • Transient- This situation or link is created while the closing interaction is executed, but destroyed before the execution is completed
Common Modeling Techniques
Modeling a Flow of Control 
To model a flow of control: 
  • Determine what interaction must be modeled 
  • Analyze which objects take part in the interaction, set their initial properties, which includes their attribute values, state, and role 
  • If the model highlights the structural organization of these objects, identify the links that associate them which are relevant to the paths of communication 
  • Indicate the nature of the links using the UMLs standard stereotyped and constraints wherever necessary 
  • Specify the messages from object to object in time order 
  • Distinguish the different kind of messages wherever necessary. Also, include parameters and return values to pass on the interaction details 
  • Enhance each object with its state and role at every stage in time
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Interaction at a Glance
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