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Behavioral models.docx

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Information Technology Management
ITM 305
Jim Tam

Chapter 6 Behavioural Models Behavioural models Behavioral models describe the internal dynamic aspects of an information system that supports the business process in an organization Introduction  Two types of behavioral models  First, there are behavioral models that are used to represent the underlying details of a business process portrayed by a use case model.  Second, there is a behavioral model that is used to represent the changes that occur in the underlying data. Behavioral models  When an analyst is attempting to understand the underlying domain of a problem, he or she must consider both structural and behavioral aspects of the problem.  By viewing the problem domain as a set of use cases that are supported by a set of collaborating objects, object oriented approaches allow the analyst to minimize the semantic gap between the real world set of objects and the evolving object-oriented model of the problem. Interaction diagrams  The modeling focus on the class diagram is at the class level,, while the interaction diagrams focus on the object level. Objects, operations, and messages  Each object has attributes that describe information about the object, such as the patient’s name, birth date, address, and phone number.  Each object has behaviors.  The behaviors are described by operations.  An operations, is nothing more than an action that an object can perform/  Each object can send and receive messages; messages are information sent to objects to tell an object to execute one of its behaviors. Sequence Diagrams  Two types of interaction diagrams.  They illustrate the objects that participate in a use case and the messages that pass between them.  The sequence diagram can be a generic sequence diagram that shows all the possible scenarios.  Instance diagrams, each of which depicts a single scenario within the use case. 1 Chapter 6 Behavioural Models Elements of sequence diagram  Actors and objects that participate in the sequence are placed across the top of the diagram using actor symbols.  A dotted line runs vertically below each actor and object to denote the lifetime of the actors/objects over time.  Temporary objects, and in this case an X is placed at the end of the lifeline.  A thin rectangular box, called the execution occurrence, is overlaid onto the lifeline to show when the class are sending and receiving messages.  A message is a communication between objects.  Operation call messages pass between classes are shown using solid lines connecting two objects with an arrow on the line showing which way the message is being passed.  A return message is depicted as a dashed line with an arrow on the end of the line portraying the direction of the return.  At times a message is sent only if a condition is met. Building a sequence diagram  A six step process used to create a sequence diagram.  The first step in the process is to determine the context of the sequence diagram.  The second step is to identify the objects that participate in the sequence being modeled.  The third step is to set the lifeline for each object, to do this; you need to draw a vertical dotted line below each class to represent the class’s existence during the sequence.  The fourth step is to add the messages to the diagram; this is done by drawing arrows to represent the messages being passed from object to object.  The fifth step is to place the execution occurrence on each object’s lifeline by drawing a narrow rectangle box over top the lifelines to represent when the classes are sending and receiving messages.  The sixth step is to validate the sequence diagram. Communication diagrams  Essentially provide a view of the dynamic aspects of an object-oriented system.  Essentially an object diagram that shows message passing relationships, instead of aggregation or generalization associations.  Communication dia
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