CMPT 275 Phase: Design
Contents
1. CMPT 275 Phase Design Map of design phase DESIGN ey as HIGH LEVEL DESIGN DESIGN pata ge Persistance Subsystem Module Interfaces Classes Class Interfaces Modularization Inietacnen Diagrams architecture Ser Interface User Manual Implementation Janice Regan 2008 Map of design phase DESIGN LOW LEVEL HIGH LEVEL DESIGN DESIGN aon Data we Persistant Subsystem Module Interfaces Classes Interaction Diagrams Modularization Class Interfaces architecture Ser Interface User Manual Implementation Janice Regan 2008 3 Design phase High level design product or system design Architecture Definition of subsystems Description of interaction of subsystems Low level design design of classes objects Attributes Data structures Methods Algorithms Janice Regan 2008 Sub Phase Low Level Design Sequence Diagrams Low Level Design Objective of Low Level Design Refine representation models of software system to a level of detail that will allow resulting representation to be used as a blueprint for implementation and unit test planning phases Janice Regan 2008 Modeling at different phases Static Dynamic 1 System Context Diagram 2 Informal Scenarios 3 Class Di2. Postconditions User record is updated in the Database Exceptional flow of events 1 sample of exceptional flows The User cancels the use case at any point prior to indicating that they have completed the editing by pressing the cancel button The Database is not altered Janice Regan 2008 Be careful with preconditions This previous use case specifies that the user has reached the web site It does not specify that the user has been validated by the security system The use case indicates that the user will be able to validate their identity after choosing to update their profile using an lt lt include gt gt The first UI screen on the website will show update profile as a choice The screen resulting from that choice will contain the validate identity button Janice Regan 2008 Be careful with preconditions If the use case specified that the user must have already validated themselves then The first UI screen would be validation e g login and validation would be a separate use case and sequence diagram used only at login The second or later UI screen would allow the user to choose the option of updating their profile BE SURE TO BE CONSISTENT IN YOUR DESIGN Janice Regan 2008 16
3. q_ message retumvaluet Synchronous Message wait for reply then continue reply explicitly shown will return returnvaluel at end of activation box started by the message return message illustrated Janice Regan 2008 Messages and returns object1 Classi returnvalue1 message1 parameter1 message2 parameter2 a returnvalue3 message3 parameter3 ia message2 returnvalue2 Message can be an actual message or it may be an invocation of the methods of the destination class Janice Regan 2008 15 Sending messages conditionally object1 Classi object2 Class2 parameter1 gt 23 returnvalue1 message parameter i Message is sent only if the condition in the square brackets is true For this example the condition in the square brackets requires the value of parameter gt 23 Janice Regan 2008 Sending messages repeatedly object1 Classi parameter1 gt 23 returnvalue1 message1 parameter1 Message is sent if the condition in the square brackets is true the message is sent repeatedly until the condition in the square brackets becomes false Usually used to send the same message to many objects Janice Regan 2008 Reflexive message object Class1 When an object sends a message to itself this message is a reflexive message Janice Regan 2008 Sequence Diagram Format
4. 3 7 Creation object Class lt lt create gt gt 8 Destruction object Class object Class lt lt lt lt destroy gt gt Janice Regan 2008 Create and destroy object1 Classi object2 Class2 Janice Regan 2008 Sequence Diagram Format 4 9 Algorithm details on left most part Actor Name of diagram Algorithm 10 Scenario Use Case name and functional requirement Janice Regan 2008 Sequence Diagram How to Objects that exist initially are lined up along the top of the diagram beside the actor When object is created later its box appears further down at the time when it is created Actor initiates interaction via GUI this is the first message sent Reception of a message by an object causes one of its methods to be executed Janice Regan 2008 2 Refined Scenario 1 Use Case Name CheckInResource 7 Scenario Student Patron Paul returns a book on time Preconditions Librarian Eva has successfully gained access to the LMS LMS is ready to go DB has been populated network is up and LMS has been initialized LMS screen with Check menu is displayed Janice Regan 2008 Refined Scenario 1 Main flow of events 1 Student Patron Paul comes up to the librarian counter to return the Quantum Physics book he borrowed last we
5. new scenario Pressing cancel implies that nothing in the database will be changed If cancel were pressed rather than done we would have to undo the changes to the database Janice Regan 2008 Consider other scenarios What if librarian Eva decides not to press done and confirm the check in of the book but chooses to press cancel and terminate the interaction instead If cancel were pressed rather than done we would have to undo the changes to the database This is clearly extra work want to ask if done before the database is updated then only update if done is pressed Need to refine the use case and the interaction diagram to handle both scenarios Janice Regan 2008 33 11 Refined Scenario 1 Main flow of events Since Student Patron Paul is returning the uantum Physics book before its due date there is no overdue charge Also no one is currently requesting the Quantum Physics book LMS completes the check in process by changing the status of the book to reshelve a canceling its due date and date of loan a updating its date of return to today ef Clearing the borrowing patron ID ea removing the Quantum Physics book from the Student Patron Paul s list of borrowed resources Janice Regan 2008 34 Refined Scenario 1 LMS updates its internal records for the Quantum Physics book and the borrowing Studen
6. agram 4 Use cases 5 Use cases Diagrams 6 Scenarios Requirements analysis 8 Analyze data persistence 7 Architecture from 1 4 5 6 i rehitecture from 9 Refined use cases from 4 7 8 High Level Design 11 Refined Class Diagram 12 Refined use cases and scenarios Low Level including attributes and from 9 Design methods from 3 12 13 13 Sequence Diagrams and collaboration diagrams from 12 Janice Regan 2008 Interaction Diagrams Model dynamic aspects of the software system by specifying the interaction among objects to produce a particular behaviour For each use case Show object interaction Show how software system realizes a use case Help identify object operations methods Janice Regan 2008 8 Interaction Diagrams Two types of interaction diagrams are defined in UML Collaboration diagram emphasizes the structural organization of objects that send and receive messages Sequence diagram emphasizes the time ordering of the messages passed between objects However both diagrams are not computationally complete they are not algorithms gt They do not define the behaviour Janice Regan 2008 Sequence Diagram Format 1 1 Initiating actor at top left initiating actor 2 _ followed by boxes representing objects zoas Jor object Class Or Module Name Synchronous Mes
7. d 0 lI Remove QPBook from list of borrowed resources display checkInPage lok update QPBook Display startpage ok update paul Inter Subsystem Interface Description Goal To illustrate dynamic relationships between subsystems and to begin to define what the interfaces of each must be Help us understand what functionality must reside in which subsystem Will eventually allow subsystems to be implemented separately and in parallel Janice Regan 2008 13 Inter Subsystem Interface Description Describe interactions Between software system and human users Between subsystems of the software system Between distributed processes encompassed in a subsystem over a network Between software system and solutions for data persistence e g database management systems Can be seen as public interface of module Janice Regan 2008 Modelling Inter Subsystem Interaction Interaction diagrams Sequence Collaboration Model dynamic aspects of the software system Specify interaction among entities Can be refined during low level design Sequence Diagram Emphasizes time ordering of interactions Collaboration Diagram Emphasizes structural organization of the objects that are interacting Janice Regan 2008 Sequence Diagram 1 sequence diagram per use case Specify sp
8. ecialized communication protocol such as Common Gateway Interface CGI protocol Hypertext Transport Protocol HTTP Janice Regan 2008 14 System Context Diagram Database Janice Regan 2008 Architecture Application AN weiner User Interface i Database interface Persistent Storage Here the database is available to the Application In this representation the Database is not part of the application Database but an external software product barize neseg used by the application Use case for Web application Use case name Edit Profile functional requirement 3 Initiating actor User Preconditions DB populated system running User reached Web site Main flow of events The User requests to edit her his profile by pressing the Edit Profile button on the Web page The User validly identifies her himself to the system through the Identify use case identify will shown as an lt lt include gt gt in use case diagram The User s profile is retrieved from the Database and is displayed on the web page The User updates her his profile information specify information Janice Regan 2008 Use case for Web application The User indicates that s he is done by pressing the Commit button The system stores the updated information to the Database and the use case terminates
9. ek Eva the Librarian chooses CheckInResource option from the LMS screen by selecting the In command option under the Check menu A window representing a Check In Form is then displayed Janice Regan 2008 Refined Scenario 1 Main flow of events cont 4 Eva takes the book Paul is handing to her and types in its Dewey call number in the appropriate text field then presses the Accept button to commit the entry The Dewey call number for the book was entered successfully and it was a valid call number information about the Quantum Physics book and the borrowing patron is retrieved from the Database and displayed on the Check In screen Janice Regan 2008 Refined Scenario 1 Main flow of events cont Since Student Patron Paul is returning the Quantum Physics book before its due date there is no overdue charge Also no one is currently requesting the Quantum Physics book LMS completes the check in process by 1 changing the status of the book to reshelve 1 canceling its due date and date of loan updating its date of return to today Clearing the borrowing patron ID removing the Quantum Physics book from the Student Patron Paul s list of borrowed resources Janice Regan 2008 Refined Scenario 1 Main flow of events cont LMS updates the records for the Quantum Physics book and the borrowing Stude
10. nt Patron Paul in the Database LMS updates the screen showing the newly checked in book along with the updated dates Eva verifies by looking at the screen that the book has been checked in properly then presses the Done button Janice Regan 2008 Refined Scenarios 1 Postconditions Student Patron Paul s record is now showing that he is no longer borrowing the Quantum Physics book The Quantum Physics book has now a Status of reshelve today s date as a date of return date of loan has been cleared and so has the due date Janice Regan 2008 Sequence Diagram 0 Librarian checkinPage Dis name getNam lexpiryDate getExpiryDate Sequence Diagram 1 ra mser 10 Sequence Diagram 2 A n lok checkin date Set status reshelve Set loan date 0 Set due date 0 Set return date today date Set borrowing patron id 0 i Remove QPBook from list of borrowed resources update paul CA i update ok F display checkinPage Display startpage Consider other scenarios What if librarian Eva decides not to press done and confirm the check in of the book but chooses to press cancel and terminate the interaction instead Look at sequence diagram 2A what needs to change for this
11. sage wait for reply then continue Asynchronous Message continue without waiting for reply Implicit return at end of activation Janice Regan 2008 UML Notational Elements of Interaction Diagrams Note An object is distinguished from a class in UML notation by the colon An object name is optional Multiple objects of same class may participate in behaviour A link between 2 objects implies an association between their classes in Class Diagram Janice Regan 2008 Sequence Diagram Format 2 6 Life line indicating when object z is available 7 Activation box indicates when object is active receiving messages doing some activity although the diagram may not specify this sending messages Janice Regan 2008 Sequence Diagram Format 3 F 8 Labels on leftmost part of diagram Indicate actions such as Actor Name other use cases being initiated actor interacting with the UI Identify use case executed These actions are not expressed by an arrow in the diagram since they do not represent inter module communication Profile altered Janice Regan 2008 Representing messages returnvalue1 message1 parameter1 Synchronous Message wait for reply then continue reply implicit will return returnvalue1 at end of activation box started by the message not shown in diagram message1 parameter1
12. t Patron Paul LMS updates the screen showing the newly checked in book along with the updated dates from its internal records Eva verifies by looking at the screen that the book has been checked in properly then presses the Done button The changes to the records for the Quantum Physics book and the borrowing Student Patron Paul are updated in the database Janice Regan 2008 Updated Sequence Diagram 2 A Librarian display checkinPage LibrarySystem lQPBook Book Paul Student db LibraryDB flag done ok Set status reshelve Set loan date 0 Set due date 0 Set return date today date Set borrowing patron id 0 Remove QPBook from list of borrowed resources update paul _ gt heckin ok fe Display startpage cheaun c ri update ok Sequence Diagram 2 B gisplay checkinPage Press done or i cancel flag done ok chepkin date Set status reshelve Set loan date 0 Set due date 0 Set return date today date Set borrowing patron id 0 Remove QPBook from list of borrowed resources Display startpage Sequence Diagram 2 C Librarian Set status reshelve Set loan date 0 Set due date 0 Set return date today date Set borrowing patron i
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