Lecture11 use case sequence diagram

Editor's Notes

• #3: 1) Sequence diagram Emphasize explicit chronological sequence of messages Useful in situations where the order in which events occurs is important WE ARE BUILDING ONLY SEQUENCE DIAGRAMS; helpful in seeing if you have all the methods for the different classes 2) Collaboration diagrams Emphasize the relationship between objects Powerful tool for understanding the structure of the software product Events are represented by annotated arrows placed alongside lines connecting boxes containing the names of actors
• #4: 1) Sequence diagram Emphasize explicit chronological sequence of messages Useful in situations where the order in which events occurs is important WE ARE BUILDING ONLY SEQUENCE DIAGRAMS; helpful in seeing if you have all the methods for the different classes 2) Collaboration diagrams Emphasize the relationship between objects Powerful tool for understanding the structure of the software product Events are represented by annotated arrows placed alongside lines connecting boxes containing the names of actors
• #5: In 3350, each team MUST CREATE SEQUENCE DIAGRAM FOR NORMAL SCENARIO FOR EACH USE CASE ON USE CASE DIAGRAM Sequence Diagram Used to document the details of a use case Shows the sequence of messages that implement a service or transaction Class diagram has a modeling focus on the class level while sequence diagram has a modeling focus is on the object level Represents a scenario from a use case Is a graphical representation of interactions between objects showing the sending and receiving of messages in sequence Emphasize the time-based ordering of the activity that takes place among a set of objects Used to understand the flow of control of a scenario by time Depicts the objects and classes involved in the scenario and the sequence of messages exchanged between the objects needed to carry out the functionality of the scenario
• #6: In a sequence diagram Each column represents an object that is participating in the interaction. The vertical axis represents time (from top to bottom). Messages are shown by full arrows. Labels on full arrows represent message names and arguments. The operation can itself send other requests to other objects An object can request an operation from itself (looping arrow) Activations the time it takes to perform an operation are depicted by a rectangle attached to an object. The height of the rectangle is indicative for the duration of the operation The vertical rectangle shows that an object is active, that is, it is handling a request made by another object.
• #8: Sequence Diagram Shows the sequence of messages that implement a service or transaction Class diagram has a modeling focus on the class level while sequence diagram has a modeling focus is on the object level Emphasize the time-based ordering of the activity that takes place among a set of objects Used to understand the flow of control of a scenario by time Depicts the objects and classes involved in the scenario and the sequence of messages exchanged between the objects needed to carry out the functionality of the scenario
• #9: Object in a sequence diagram Still represented by the rectangle with object name on inside
• #10: 3 ways to name: Just an object name Object name and class name Just a class name Object names are always underlined and begin with a lowercase letter Class names are always capitalized Naming objects Name classes consistently with your class diagram (same classes). Include instance names when objects are referred to in messages or when several objects of the same type exist in the diagram. Most of the time you use the class name, but if you refer to a particular instance in a scenario the object:Class notation is used. Objects can be named by Using generic object names to clarify the class Including the name of the class after the name of the object, separated by a colon
• #11: Actor in a Sequence diagram Still represented by the stick figure as on use case diagram don’t have to place in any particular order across the top of the diagram but better to organize them in the order in which they participate in the sequence Illustrating actors as active objects models how actors interact with the system and how the system interacts with the user Actors can call objects and objects can notify actors
• #13: Messages An interaction between two objects is performed as a message sent from one object to another. HOW ACTIVE OBJECTS COMMUNICATE WITH EACH OTHER IN A SEQUENCE DIAGRAM Illustrate the flow between the objects, how they interact, and what conditions change the flow
• #14: Time required by the receiver object to process the message is denoted by focus of control
• #15: 3) Flat Use when we don’t care and don’t know if a message is synchronous or asynchronous NOTICE THAT THE ARROW HEAD IS ONLY 2 LINES, NOT A FILLED-IN TRIANGLE
• #16: Synchronize Messages The object :A is in a hold pattern waiting for the response from the object :B Indicates that flow is interrupted until the message has completed, and any messages that were sent from that message are completed as well. Used for procedural system flow where one piece of functionality is executed before another Modeled with a solid arrow head and line
• #17: Asynchronous messages Used when control flow does not need to be interrupted before completing Can be used for modeling concurrent systems Can: Create a new thread (a new activation record) Create a new object Communicate with a thread that is already running Active objects own an execution thread and can initiate control activity.
• #19: In a sequence diagram Each column represents an object that is participating in the interaction. The vertical axis represents time (from top to bottom). Messages are shown by full arrows. Labels on full arrows represent message names and arguments. The operation can itself send other requests to other objects An object can request an operation from itself (looping arrow) Activations the time it takes to perform an operation are depicted by a rectangle attached to an object. The height of the rectangle is indicative for the duration of the operation The vertical rectangle shows that an object is active, that is, it is handling a request made by another object.
• #21: Lifeline in a sequence diagram Represented by a vertical line for which our book uses a dotted (dashed) line or other people use a solid line Sometimes an object creates a temporary object and in this case an X is placed at the end of the object’s lifeline to show that it is going out of existence (is destroyed) Example: shopping cart object for a Web commerce application which is no long needed while the order is placed If objects exist in the system after they are used in the sequence diagram, their lifeline continues to the bottom of the diagram
• #22: A focus of control in a sequence diagram Shows the period of time in which an object has a thread of control
• #23: In a sequence diagram Each column represents an object that is participating in the interaction. The vertical axis represents time (from top to bottom). Messages are shown by full arrows. Labels on full arrows represent message names and arguments. The operation can itself send other requests to other objects An object can request an operation from itself (looping arrow) Activations the time it takes to perform an operation are depicted by a rectangle attached to an object. The height of the rectangle is indicative for the duration of the operation The vertical rectangle shows that an object is active, that is, it is handling a request made by another object.
• #24: Conditional messages: A message might contain a guard condition denoted in square brackets
• #27: The branch represents concurrency if the guard conditions are mutually inclusive. Thus multiple messages are sent.
• #31: People differ on how to different parts of the UML diagrams In little UML book, Ambler (author) says that introducing object destruction often introduces clutter to the diagram
• #33: Steps for building a sequence diagram 1) Set the context Determine the context of the sequence diagram Context of the diagram can be a system, a use case, a scenario of a use case, or an operation of a class MOST COMMONLY, one use-case scenario 2) Identify which objects/actors will participate Review the use case scenario and identify objects/actors Objects are also found in the class diagrams May uncover new classes/objects during this process 3) Set the lifeline Draw vertical below each actor/object to represent its existence during the sequence Place an X below an object at the point on the lifeline where the object goes out of existence 4) Lay out messages Draw arrows to represent the messages being passed from object to object, with the arrow pointing in the message’s transmission direction Review the use case scenario and look for communication between objects and actors OR objects and other objects Identify senders and receivers of messages Arrows should be placed in order from the first message (at the top) to the last (at the bottom) to show time sequence Put name of operation to be invoked on top of arrow line (add arguments if known) 5) Add focus of control Draw a narrow rectangular box over the top of the lifelines to represent when the actors or classes are sending and receiving messages 6) Validate Guarantee that the diagram depicts all of the steps in the process
• #34: Steps for building a sequence diagram 1) Set the context Determine the context of the sequence diagram Context of the diagram can be a system, a use case, a scenario of a use case, or an operation of a class MOST COMMONLY, one use-case scenario 2) Identify which objects/actors will participate Review the use case scenario and identify objects/actors Objects are also found in the class diagrams May uncover new classes/objects during this process 3) Set the lifeline Draw vertical below each actor/object to represent its existence during the sequence Place an X below an object at the point on the lifeline where the object goes out of existence 4) Lay out messages Draw arrows to represent the messages being passed from object to object, with the arrow pointing in the message’s transmission direction Review the use case scenario and look for communication between objects and actors OR objects and other objects Identify senders and receivers of messages Arrows should be placed in order from the first message (at the top) to the last (at the bottom) to show time sequence Put name of operation to be invoked on top of arrow line (add arguments if known) 5) Add focus of control Draw a narrow rectangular box over the top of the lifelines to represent when the actors or classes are sending and receiving messages 6) Validate Guarantee that the diagram depicts all of the steps in the process
• #35: Steps for building a sequence diagram 1) Set the context Determine the context of the sequence diagram Context of the diagram can be a system, a use case, a scenario of a use case, or an operation of a class MOST COMMONLY, one use-case scenario 2) Identify which objects/actors will participate Review the use case scenario and identify objects/actors Objects are also found in the class diagrams May uncover new classes/objects during this process 3) Set the lifeline Draw vertical below each actor/object to represent its existence during the sequence Place an X below an object at the point on the lifeline where the object goes out of existence 4) Lay out messages Draw arrows to represent the messages being passed from object to object, with the arrow pointing in the message’s transmission direction Review the use case scenario and look for communication between objects and actors OR objects and other objects Identify senders and receivers of messages Arrows should be placed in order from the first message (at the top) to the last (at the bottom) to show time sequence Put name of operation to be invoked on top of arrow line (add arguments if known) 5) Add focus of control Draw a narrow rectangular box over the top of the lifelines to represent when the actors or classes are sending and receiving messages 6) Validate Guarantee that the diagram depicts all of the steps in the process
• #36: Steps for building a sequence diagram 1) Set the context Determine the context of the sequence diagram Context of the diagram can be a system, a use case, a scenario of a use case, or an operation of a class MOST COMMONLY, one use-case scenario 2) Identify which objects/actors will participate Review the use case scenario and identify objects/actors Objects are also found in the class diagrams May uncover new classes/objects during this process 3) Set the lifeline Draw vertical below each actor/object to represent its existence during the sequence Place an X below an object at the point on the lifeline where the object goes out of existence 4) Lay out messages Draw arrows to represent the messages being passed from object to object, with the arrow pointing in the message’s transmission direction Review the use case scenario and look for communication between objects and actors OR objects and other objects Identify senders and receivers of messages Arrows should be placed in order from the first message (at the top) to the last (at the bottom) to show time sequence Put name of operation to be invoked on top of arrow line (add arguments if known) 5) Add focus of control Draw a narrow rectangular box over the top of the lifelines to represent when the actors or classes are sending and receiving messages 6) Validate Guarantee that the diagram depicts all of the steps in the process
• #37: Steps for building a sequence diagram 1) Set the context Determine the context of the sequence diagram Context of the diagram can be a system, a use case, a scenario of a use case, or an operation of a class MOST COMMONLY, one use-case scenario 2) Identify which objects/actors will participate Review the use case scenario and identify objects/actors Objects are also found in the class diagrams May uncover new classes/objects during this process 3) Set the lifeline Draw vertical below each actor/object to represent its existence during the sequence Place an X below an object at the point on the lifeline where the object goes out of existence 4) Lay out messages Draw arrows to represent the messages being passed from object to object, with the arrow pointing in the message’s transmission direction Review the use case scenario and look for communication between objects and actors OR objects and other objects Identify senders and receivers of messages Arrows should be placed in order from the first message (at the top) to the last (at the bottom) to show time sequence Put name of operation to be invoked on top of arrow line (add arguments if known) 5) Add focus of control Draw a narrow rectangular box over the top of the lifelines to represent when the actors or classes are sending and receiving messages 6) Validate Guarantee that the diagram depicts all of the steps in the process
• #38: Steps for building a sequence diagram 1) Set the context Determine the context of the sequence diagram Context of the diagram can be a system, a use case, a scenario of a use case, or an operation of a class MOST COMMONLY, one use-case scenario 2) Identify which objects/actors will participate Review the use case scenario and identify objects/actors Objects are also found in the class diagrams May uncover new classes/objects during this process 3) Set the lifeline Draw vertical below each actor/object to represent its existence during the sequence Place an X below an object at the point on the lifeline where the object goes out of existence 4) Lay out messages Draw arrows to represent the messages being passed from object to object, with the arrow pointing in the message’s transmission direction Review the use case scenario and look for communication between objects and actors OR objects and other objects Identify senders and receivers of messages Arrows should be placed in order from the first message (at the top) to the last (at the bottom) to show time sequence Put name of operation to be invoked on top of arrow line (add arguments if known) 5) Add focus of control Draw a narrow rectangular box over the top of the lifelines to represent when the actors or classes are sending and receiving messages 6) Validate Guarantee that the diagram depicts all of the steps in the process
• #39: Steps for building a sequence diagram 1) Set the context Determine the context of the sequence diagram Context of the diagram can be a system, a use case, a scenario of a use case, or an operation of a class MOST COMMONLY, one use-case scenario 2) Identify which objects/actors will participate Review the use case scenario and identify objects/actors Objects are also found in the class diagrams May uncover new classes/objects during this process 3) Set the lifeline Draw vertical below each actor/object to represent its existence during the sequence Place an X below an object at the point on the lifeline where the object goes out of existence 4) Lay out messages Draw arrows to represent the messages being passed from object to object, with the arrow pointing in the message’s transmission direction Review the use case scenario and look for communication between objects and actors OR objects and other objects Identify senders and receivers of messages Arrows should be placed in order from the first message (at the top) to the last (at the bottom) to show time sequence Put name of operation to be invoked on top of arrow line (add arguments if known) 5) Add focus of control Draw a narrow rectangular box over the top of the lifelines to represent when the actors or classes are sending and receiving messages 6) Validate Guarantee that the diagram depicts all of the steps in the process
• #42: Steps for building a sequence diagram 1) Set the context Determine the context of the sequence diagram Context of the diagram can be a system, a use case, a scenario of a use case, or an operation of a class MOST COMMONLY, one use-case scenario 2) Identify which objects/actors will participate Review the use case scenario and identify objects/actors Objects are also found in the class diagrams May uncover new classes/objects during this process 3) Set the lifeline Draw vertical below each actor/object to represent its existence during the sequence Place an X below an object at the point on the lifeline where the object goes out of existence 4) Lay out messages Draw arrows to represent the messages being passed from object to object, with the arrow pointing in the message’s transmission direction Review the use case scenario and look for communication between objects and actors OR objects and other objects Identify senders and receivers of messages Arrows should be placed in order from the first message (at the top) to the last (at the bottom) to show time sequence Put name of operation to be invoked on top of arrow line (add arguments if known) 5) Add focus of control Draw a narrow rectangular box over the top of the lifelines to represent when the actors or classes are sending and receiving messages 6) Validate Guarantee that the diagram depicts all of the steps in the process