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SE - Lecture 6 - Software Design n Construction.pptx

The document discusses sequence diagrams, which are used to model the interactions between objects in a system. It provides details on the components and structure of sequence diagrams, including objects, messages, time ordering, and scenarios. Sequence diagrams show objects arranged from left to right and messages sent between objects over time from top to bottom.

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ITS 66404 Principles of Software Engineering Nur Haifa Chapter 6- Software Design and Construction Sequence Diagram
Agenda ✧ Software Development phases ✧ Software Lifecycle activities ✧ Software Design ✧ Software Construction ✧ Sequence Diagram Chapter 1 – Intro to Software Engineering 2
3 Software Development Phases Requirements What needs to be done Analysis How it should be done Design Create a software structure (architecture) around which code will be built Construction Fill in the software structure with code Testing Check that the code does what it is supposed to (functionality, performance, reliability, …) Project Management Devise a plan, manage resources, costs, time, …
4 Software Phases Related to this Course Design Create a software structure (architecture) around which code will be built Construstion Fill in the software structure with code
5 Design Create a software structure (architecture) around which code will be built
Introduction to Software Design 6 Software Life Cycle Activities Defined
7 Software Life Cycle Activities (more) ✧Requirements Specification ▪ System analyst works with users to clarify the detailed system requirements ▪ Questions include format of input data, desired form of any output screens, and data validation ✧Analysis ▪ Make sure you completely understand the problem before starting the design or program a solution ▪ Evaluate different approaches to the design
Chapter 1: Introduction to Software Design 8 Software Life Cycle Activities (continued) ✧Design Modelling ▪ Top-down: break system into smaller subsystems ▪ Object-oriented: identify objects and their interactions ▪ UML diagrams: tool to show interactions between: • Use case diagram • Class diagram • Object diagram • Sequence diagram • Activity diagram • State diagram
Chapter 1: Introduction to Software Design 9 Example of Top-Down: Stepwise Refinement
10 Construstion Fill in the software structure with code
Software Construction 11 Construction Definition of Software Construction: Detailed creation of working, meaningful software through a combination of coding, verification, unit testing, integration testing, and debugging Software construction closely tied to ▪ Software design ▪ Software testing Design Construction Testing 5/9/2021
Software Construction 12 More on Construction ✧ Significant detailed design occurs during construction ✧ Low-level (e.g. unit and module integration) testing occurs during construction ✧ Construction produces high volume of configuration items ▪ Thus construction linked to configuration management ✧ Construction is tool intensive ✧ Quality (or lack thereof) is very evident in the construction products ✧ Construction highly related to Computer Science due to ▪ Use of algorithms ▪ Detailed coding practices 5/9/2021
Software Construction 13 The fundamentals of software construction include: ▪ Minimizing complexity ▪ Anticipating change ▪ Constructing for verification ▪ Standards in construction The following slides discuss each of these fundamentals 5/9/2021 Software Construction Fundamentals
Software Construction 14 Minimizing Complexity ✧ Humans are severely limited in our ability to hold complex information in our working memories ✧ As a result, minimizing complexity is one the of strongest drivers in software construction ✧ Need to reduce complexity throughout the lifecycle ✧ As functionality increases, so does complexity ✧ Accomplished through use of standards ✧ Examples: ▪ J2EE for complex, distributed Java applications ▪ UML for modeling all aspects of complex systems ▪ High-order programming languages such as C++ and Java ▪ Source code formatting rules to aid readability 5/9/2021
Software Construction 15 Anticipating Change ✧ Software changes over time ✧ Anticipation / hope of change affect how software is constructed ✧ This can effect ▪ Use of control structures ▪ Handling of errors ▪ Source code organization ▪ Code documentation ▪ Coding standards 5/9/2021
Software Construction 16 Constructing for Verification Construct software that allows bugs to be easily found and fixed Examples: ✧ Enforce coding standards ▪ Helps support code reviews ✧ Unit testing ✧ Organizing code to support automated testing ✧ Restricted use of complex or hard-to-understand language structures 5/9/2021
Software Construction 17 Standards in Construction Standards which directly affect construction issues include: ✧ Programming languages ▪ E.g. standards for languages like Java and C++ ✧ Communication methods ▪ E.g. standards for document formats and contents ✧ Platforms ▪ E.g. programmer interface standards for operating system calls, J2EE ✧ Tools ▪ E.g. diagrammatic standards for notations like the Unified Modeling Language 5/9/2021
✧ Sequence Diagram 5/9/2021 18
Sequence diagrams ✧ Sequence diagrams are part of the UML and are used to model the interactions between the actors and the objects within a system. ✧ A sequence diagram shows the sequence of interactions that take place during a particular use case or use case instance. ✧ The objects and actors involved are listed along the top of the diagram, with a dotted line drawn vertically from these. ✧ Interactions between objects are indicated by annotated arrows. 19 5/9/2021
Creating interaction diagrams You should develop a class diagram and a use case model before starting to create an interaction diagram. ▪ There are two kinds of interaction diagrams: • Sequence diagrams • Communication diagrams
Objects Interact with Messages ✧ A message shows how one object asks another object to perform some activity. : Car buyer :RegistrationController :CourseCatalogSystem getCourseOfferings(forSemester) Message
What Is a Sequence Diagram? ✧ A sequence diagram is an interaction diagram that emphasizes the time ordering of messages. ✧ The diagram shows: ▪ The objects participating in the interaction. ▪ The sequence of messages exchanged. Sequence Diagram
Sequence Diagram Contents: Objects :RegisterForCoursesForm :RegistrationController SWTSU Catalog : CourseCatalogSystem Anonymous Objects Lifelines Named Object
:RegisterForCours esForm :RegistrationCo ntroller SWTSU Catalog : CourseCatalogS ystem : Student Sequence Diagram Contents: Actor Actor instances :Course Catalog
Sequence Diagram Contents: Messages Reflexive Messages 1: create schedule( ) 2: get course offerings( ) 3: get course offerings(for Semester) 4: get course offerings( ) : Student : Course Catalog 6: display blank schedule( ) 5: display course offerings( ) Message :RegisterForCours esForm :RegistrationCo ntroller SWTSU Catalog : CourseCatalogS ystem
1: create schedule( ) 2: get course offerings( ) 3: get course offerings(for Semester) 4: get course offerings( ) 6: display blank schedule( ) :RegisterForCoursesForm :RegistrationController SWTSU Catalog : CourseCatalogSystem : Student : Course Catalog Sequence Diagram Contents: Execution Occurrence Execution Occurrence 5: display course offerings( )
1: create schedule( ) 2: get course offerings( ) 3: get course offerings(for Semester) 4: get course offerings( ) 6: display blank schedule( ) Sequence Diagram Contents: Event Occurrence Event Occurrence 5: display course offerings( ) :RegisterForCours esForm :RegistrationCo ntroller SWTSU Catalog : CourseCatalogS ystem : Student :Course Catalog
Scenario Scenarios are used to describe how use cases are realized as interactions among societies of objects. A scenario is an instance of a use case; it is one path through the flow of events for use case. Scenarios are developed to help identify the objects, the classes, and the objects interactions needed to carry out a piece of functionality specified by the use case.
objectName objectName : ClassName : ClassName Object name Object name and class Class name 3 Naming Conventions for Objects
objectName Representing an object in an sequence diagram
Messages Message that go from one object to another goes from one object timeline to the other object’s timeline. An object can send s message to itself – that is, from its timeline back to its own timeline – A message can be return, synchronous, or asynchronous
A synchronous message is when an object sends a message, and waits for an answer to that message before it proceeds with its business Synchronous An asynchronous message is when an object sends a message, and does not wait for an answer before it proceeds Asynchronous Return Not a message but a return from the earlier message Notations
Time The sequence diagram represents time in the vertical direction. Time starts at the top and progresses toward the bottom. A message that’s closer to the top occurs earlier in time than a message that’s closer to the bottom. The sequence diagram is two-dimensional. The left-to- right dimension is the layout of the objects, and the top-to- bottom dimension that shows the passage of time
objectName1 objectName2
aMember: LibraryMember : LibraryMember theCopy: Copy 0. borrow(theCopy) 1. okToBorrow (< LoanLimit) 2. borrow() 3. updateAvaCopies() 4. borrowed 5. updateLoanItem() 6. confirm A Simple Sequence Diagram of Library System
Sequence Diagram - A phone system p: PhoneSystem s : Caller r : Caller 1: pick up hand set 3: beeps and sound 4: dial number 5: create connection 7b: connect(r) 6: pick up hand set 7a: connect(s) 2: insert coins 8: return coins
CDS student : Student : YearTutor Mr. TutorOfCDS choose modules confirm choice email Register for modules inform student (accept / reject) Course management
Sequence diagram for View patient information 38 5/9/2021
Sequenc e diagram for 39 5/9/2021
Summary 1. There are 3 types of messages: _________, ___________ and _________ 2. Sequence diagram shows interaction between _________. 3. A sequence diagram must always be initiated by an _____________. 4. Objects in the sequence diagram should be ideally sequenced in the order of ________, _______ and ______. 5. An object can be represented in 3 ways: ________, ________ and ____________. 6. A sequence diagram has TWO (2) dimension. The horizontal dimension represents ________ and the vertical dimension represents ____________.
THE END Question?