Lecture 14 Interaction Diagrams Kenneth M Anderson Object Oriented Analysis and Design CSCI 6448 Spring Semester 2005 Goals for this Lecture Introduce the notion of interactions within OO designs Review the UML Notation for Interaction diagrams February 24 2005 University of Colorado 2005 2 Behavioral Modeling Interactions and Interaction diagrams allow the dynamic behavior of a system to be modeled Class diagrams allow the static structure of a system to be modeled UML has two diagrams for interactions sequence diagrams collaboration diagrams February 24 2005 University of Colorado 2005 3 Interactions OO systems do not sit idle their objects are constantly interacting with each other by sending messages Formally an interaction is a behavior that comprises a set of messages exchanged among a set of objects within a context to accomplish a purpose February 24 2005 University of Colorado 2005 4 Interaction Diagrams Interaction diagrams provide a notation for specifying interactions including notations for objects links messages and sequencing Interaction diagrams allow analysis of the flow of messages in a system over time the structural relationships between objects and how messages are passed within that structure Interaction diagrams can be applied to classes operations components use cases etc February 24 2005 University of Colorado 2005 5 Quick Overview of Concepts Objects instances of classes Links instances of associations Messages a request made by one object on another object a message can only be sent across a link Sequencing messages can be sequenced by time as we shall see message order can be indicated via numbers or via a top to bottom order a sequence is valid only for a particular thread UML can specify synchronization across threads using a variety of constructs we will see these in action soon February 24 2005 University of Colorado 2005 6 Interaction Diagrams Two types of interaction diagrams sequence diagrams useful for modeling messages over time collaboration diagrams useful for modeling messages across object structures University of Colorado 2005 February 24 2005 7 Example Sequence Diagram c Client transient create time setActions a d o p ODBCProxy Transaction setValues d 3 4 setValues a CO committed destroy February 24 2005 University of Colorado 2005 focus of control lifeline 8 Example Collaboration Diagram c Client 1 create 2 setActions a d o 3 destroy link local Transaction transient global 2 1 setValues d 3 4 2 2 setValues a CO p ODBCProxy message February 24 2005 University of Colorado 2005 9 Semantic Equivalence These examples are semantically equivalent you can convert one diagram into the other with almost no loss of information however each view tends to stress different details for instance the sequence diagram shows method return information while the collaboration diagram contains information on how the objects are linked February 24 2005 University of Colorado 2005 10 Details Links A link is a path along which a message can be sent there are different types of links association the link is present due to a class association self an object can send a message to itself global a link to an object is possible because the object exists in an enclosing scope local a link to an object is possible because the object exists in a local scope parameter a link to the object is possible because the object was passed as a parameter February 24 2005 University of Colorado 2005 11 Details Messages A message is a request for action or a query for information UML supports several pre defined message types call invokes an operation on an object return returns a value to the caller send sends a signal to an object create creates an object destroy destroys an object February 24 2005 University of Colorado 2005 12 Details Message Type Example c Client p PlanningAssistant create TicketAgent setItinerary i calculateRoute route destroy notify February 24 2005 University of Colorado 2005 13 Iteration and Branching Interaction diagrams can support both iteration and branching Iteration is indicated with an asterick followed by an optional iteration expression followed by the message name indicates parallel execution dialDigit i 1 n updateAccount i i 1 n q i calculateScore Branching is indicated with a boolean condition that appears before the sequence number or message name x 0 doThis x 0 doThat See examples in class UML ref manual page 529 and 530 February 24 2005 University of Colorado 2005 14 Synchronizing Flows of Control In the previous example notify was an asynchronous message between two different flows of control Normally flows of control are associated with active objects e g threads and a designer must take care to sequence the interactions between distinct flows In collaboration diagrams you can label each flow of control with a different flow identifier but that s about it interaction diagrams have weak notations for synchronizing flows February 24 2005 University of Colorado 2005 15 Example of Multiple Flows s1 postValue s StockTicker a1 Analyst c CNNNewsFeed c1 postBreakingStory s2 postAlert m1 postAlert m AlertManager t TradingManager i2 postAlert i IndexWatcher a2 Analyst i1 postValue February 24 2005 University of Colorado 2005 How do we protect the AlertManager s postAlert routine 16 Object Transformation Objects evolve over time and this evolution can be explicitly captured in Interaction diagrams In particular the become stereotype is used to indicate that two objects in the same diagram are actually the same object at different points in time Less commonly used the copy stereotype can be used to indicate that an object is an exact copy of some other object the copies can then evolve independently These stereotypes are typically used in collaboration diagrams in sequence diagrams object evolution is shown by redrawing a new version of the object lower on its lifeline University of Colorado 2005 February 24 2005 17 Object Transformation Example association r RegistrarAgent School 2 addStudent s 1 create 3 register 3 1 getSchedule self s Student registered false s Student registered true 3 4 become 3 2 add s c1 Course association February 24 2005 3 3 add s c2 Course association University of Colorado 2005 18
View Full Document
Unlocking...