software engineering assignment

profilecomputer_science
lesson35.ppt
Home>Computer Science homework help>software engineering assignment

*

CPSC-5360, Lesson 3

*

Software Engineering (CPSC-5360),
Lesson 3 

Stefan Andrei

CPSC-5360, Lesson 3

*

*

CPSC-5360, Lesson 3

*

Overview of the Last Lecture

  • Software Development Models
  • Waterfall Model
  • Evolutionary Models
  • Incremental Model
  • Spiral Model
  • Unified Process
  • Overview of UML
  • History
  • 4 + 1 View models
  • Using UML in UP

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

Overview of this Lecture

  • Introduction to Case Studies
  • Requirement Gathering
  • Use Case Modeling
  • Domain Modeling / Business Modeling
  • Activity Diagram

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

Case Study 1: The Restaurant

  • Example developed in the Practical Object-Oriented Design With UML by Mark Priestley, chapter 4.
  • Support the day-to-day operations of restaurant by improving the processes of:
  • Making Reservations
  • Allocating Tables
  • The Current System is based on manual booking system:
  • Hand-written forms in large folder.

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

Case Study 1: The Restaurant

Current system uses manual booking sheets.

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

Case Study 1: The Restaurant

  • Three sittings (slots) in an evening
  • Booking can span more than one slot
  • Each Booking records:
  • Contact Name and Phone Number
  • Annotation made for various events:
  • Arrival of customer (Cross out record)
  • Table switch (Arrow to new table)
  • Cancellation
  • Time to vacate
  • “Walk-In” Customer

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

Case Study 1: Restaurant

  • Problems with the manual systems:
  • Slow
  • Confusing and difficult to read
  • No backup copies
  • Hard to get useful management data
  • Develop an automated computerized version.

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

Case Study 2: The Monopoly Game

  • Chosen because of its familiarity.
  • A game played almost in every country.
  • Developed in the Applying UML and Patterns by Craig Larman, Chapter 3.
  • The software version will run as simulation:
  • User starts the simulation by indicating the number of simulated players.
  • All turns are simulated with result (trace) printed.

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

Where are we now?

  • Requirement Gathering:
  • Understanding the requirements.
  • Business Modeling:
  • Understanding the problem domain.

CPSC-5360, Lesson 3

Requirements analysis

  • Requirements analysis has the greatest importance of the software development.
  • The Unified Process places a great emphasis on the capture of system requirements using use cases.
  • The requirements analysis has the ultimate goal to define the set of use case scenarios/descriptions.

*

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

Requirement: Overview

  • Early phase of the development.
  • Inputs:
  • informal specification.
  • Activities:
  • create use case model.
  • define use cases.
  • create domain model.
  • create glossary.
  • create activity diagram.

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

Use Case View

Provides a structured view of the system's functionality.

Description of how users interact with the system.

Supported by UML use case diagrams.

Serves as the starting point for all subsequent development.

Three important definitions:

Use Case

Scenario

Actor

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

Use Case and Scenarios

Use Case:

The different tasks that users can perform while interacting with the system.

Scenarios:

Are particular instances of the use case:

Basic Course of Events: normal flow.

Alternative Course of Events: optional flow.

Exceptional Course of Events: erroneous flow.

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

Actor

Roles played by users when interacting with a system, e.g.:

Receptionist (makes bookings);

Head waiter (assigns tables etc).

Individual user may play one or more roles at different times.

These roles often correspond to a certain level of access, e.g., logging into Lamar website as Staff or Student.

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

Use Case Diagram

  • UML diagram to summarize the relationship between actors and use cases.
  • Diagram Element:

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

Case Study 1: Use Cases

  • A preliminary list of use cases:

Record new booking.

Cancel a booking.

Record customer arrival.

Transfer a customer from one table to another.

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

Case Study 1: Use Case Diagram

It shows use cases, actors, and who does what.

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

Use Cases Description

A use case comprises all the possible interactions that a user can have when performing a given task.

Often a dialogue between system and user.

These are described as courses of events, or scenarios.

A full description of a use case includes:

a basic course of events;

a number of alternative and exceptional courses.

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

Basic Course of Events

Describes what happens in the ‘normal’ case.

For example, for ‘Record Booking’:

Record Booking: Basic Course of Events

Receptionist enters date of requested reservation;

System displays bookings for that date;

There is a suitable table available: Receptionist enters details (customer’s name, phone number, time of booking, number of covers, table number);

System records and displays new booking.

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

Use Case Templates

UML does not define a standard format for use case descriptions.

Various templates have been defined to structure descriptions.

Essentially a list of subheadings such as:

Name

Actors

Courses of events

CPSC-5360, Lesson 3

*

*

CPSC-5360, Lesson 3

*

Other Use Case Description Template

Receptionist enters date of requested reservation;

there is a suitable table available: Receptionist enters details (customer’s name, phone number, time of booking, number of covers, table number);

System displays bookings for that date.

System records and displays new booking.

  • This version emphasizes the exchange between user and system, e.g.:

Actor

System

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

User Interface Prototype

  • During the use case modeling activity, it is usually useful to have a rough idea of the user interface, e.g.:

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

Alternative Course of Events

Describe predicted alternative flows.

For example, if no table is available:

Record Booking – No Table Available: Alternative Course of Event

Receptionist enters date;

System displays bookings;

no table available: end of use case.

CPSC-5360, Lesson 3

*

*

CPSC-5360, Lesson 3

*

Exceptional Course of Events

Situations where a mistake has been made.

E.g., allocate a booking to a small table:

Record Booking – table too small: Exceptional course of events

receptionist enters date;

system displays bookings;

receptionist enters details;

system asks for confirmation of oversize booking;

if “no”, use case terminates with no booking made;

if “yes”, booking recorded with warning flag.

CPSC-5360, Lesson 3

*

*

CPSC-5360, Lesson 3

*

Shared Functionality

Different use cases can overlap.

E.g., ‘Record Arrival’:

Record Arrival: Basic Course of Events

head waiter enters date;

system displays bookings;

head waiter confirms arrival for booking;

system records this and updates display.

The first two steps are shared with ‘Record Booking’ (even though there is a different actor).

CPSC-5360, Lesson 3

*

*

CPSC-5360, Lesson 3

*

Use Case Inclusion

Move shared functionality to a separate use case:

Record Booking: Basic Course of Events (revised)

receptionist performs Display Bookings;

receptionist enters details;

system records and displays new booking.

Include this in other use cases, e.g.:

Display Bookings: Basic Course of Events

user enters a date;

system displays bookings for that date.

CPSC-5360, Lesson 3

*

*

CPSC-5360, Lesson 3

*

The <<include>> Dependency

UML shows inclusion as a dependency between use cases, labelled with the stereotype <<include>> on the dashed arrow:

System

CPSC-5360, Lesson 3

*

*

CPSC-5360, Lesson 3

*

Case Study 1: Use Case Diagram (Revised)

System

Display booking

CPSC-5360, Lesson 3

*

Note: Intentionally left Incomplete

*

CPSC-5360, Lesson 3

*

Actor Generalization

The last diagram shows that the Receptionist can performs the Display bookings use case independently from the Record Booking use case.

Head Waiters can also performs Display bookings use case.

Introduce a more general actor Staff to show what the other two actors have in common.

The initial actors are specializations of the general actor.

CPSC-5360, Lesson 3

*

*

CPSC-5360, Lesson 3

*

Actor Generalization Notation

System

CPSC-5360, Lesson 3

*

*

CPSC-5360, Lesson 3

*

Use Case Extension

Recording a walk-in can be described as an exceptional course of events:

someone arrives but there’s no booking recorded.

It could also be a separate use case:

a customer arrives and asks if there's a free table.

Then, it can extend ‘Record Arrival’:

even without a booking, the customer stays to eat.

CPSC-5360, Lesson 3

*

*

CPSC-5360, Lesson 3

*

Use Case Extension

Record Walk-in: Basic Course of Events:

Head waiter performs Display Bookings use case;

Head waiter enters details (time, number of covers and the table allocated to the customer);

System records and displays new booking.

Very similar to Record Arrival use case. Can we simplify?

<<Include>> dependency is inappropriate. (why?)

Record Walk-in is performed in some cases of Record Arrival, when there is no booking for the customer (but there is an available table and customer still wants to eat there).

CPSC-5360, Lesson 3

*

The ‘include’ dependency is inappropriate, because the interactions specified in ‘Record walk-in’ are not performed every time ‘Record arrival’ is performed.

Rather, ‘Record walk-in’ is performed in some cases of ‘Record Arrival’, when there is no booking for the customer, there is a suitable table free, and the customer still wants to eat there.

Why ‘include’ dependency is not appropriate?

  • The ‘include’ dependency is inappropriate, because the interactions specified in ‘Record walk-in’ use case are not performed every time ‘Record arrival’ use case is performed.
  • Rather, the ‘Record walk-in’ use case is performed in some cases of ‘Record Arrival’, when there is no booking for the customer, there is a suitable table free, and the customer still wants to eat there.
  • The ‘Record walk-in’ use case contains more details than the ‘Record arrival’ use case.

*

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

The <<extend>> Dependency

Use case extension is shown with an <<extend>> dependency.

Record walk-in optionally extends the functionality of Record arrival.

States the constraint (condition) which causes the branch off.

System

No Prior
Booking

CPSC-5360, Lesson 3

*

‘Record walk-in’ contains more details than ‘Record arrival’.

Rather, ‘Record walk-in’ is performed in some cases of ‘Record Arrival’, when there is no booking for the customer, there is a suitable table free, and the customer still wants to eat there.

*

CPSC-5360, Lesson 3

*

Case Study 1: Complete Use Case Diagram

System

CPSC-5360, Lesson 3

*

*

CPSC-5360, Lesson 3

*

Guidelines

Use case:

Should cover the full sequence of steps from the beginning of a task until the end.

Should describe the user’s interaction with the system.

Should not describe actual computations.

Should be as independent as possible from any particular user interface design.

Should only include actions in which the actor interacts with the computer.

Use case diagram should be used to supplement the use case description, not as the main artifact.

CPSC-5360, Lesson 3

*

*

CPSC-5360, Lesson 3

*

Use Cases: Strengths

  • Simple and Familiar
  • Can be understood easily by untrained personnel, e.g., the customer.
  • Involve the customer early in the development.
  • Emphasize the user goals and perspective.
  • Scale in term of sophistication and formality.

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

Use Cases: Problems

  • Care must be taken to ensure the use cases are complete and unambiguous.
  • Only actor-initiated activities are recorded.
  • Software requirement derived from use cases often mimics the manual system too closely.
  • Preventing any innovative or more efficient way to be developed.

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

Domain Modelling

Using UML diagram to construct a model of the real-world system:

Understand the problem domain.

Model recorded as a simplified class diagram.

Seamless development:

The same notation is used for analysis and design.

The design can evolve from the initial domain model.

Business modelling means to create the use case model, to define the use cases, to create the domain model, and to create the glossary.

CPSC-5360, Lesson 3

*

*

CPSC-5360, Lesson 3

*

Domain Model Notation

  • A subset of class diagram model elements are used.

Class

Association

Name

Multiplicity

Multiplicity

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

Domain Model Notation

Classes represent real-world entities.

Attributes represent the data held about entities.

Associations represent relationships between the entities.

Generalization can be used to simplify the structure of the model.

Constraints can be used to indicate conditions.

CPSC-5360, Lesson 3

*

*

CPSC-5360, Lesson 3

*

Case Study 1: Customers and Reservations

Basic business fact: customers make reservations.

CPSC-5360, Lesson 3

*

*

CPSC-5360, Lesson 3

*

Defining a Relationship

Give a name to the relationship:

use a verb so that the relationship can be read as a sentence:

A customer can make many reservations.

How many people make a reservation?

one principal contact whose details are held;

that principal contact can make more than one reservation (e.g., by postponing the time);

the expected number of diners can be modelled as an attribute of the reservation.

CPSC-5360, Lesson 3

*

*

CPSC-5360, Lesson 3

*

Case Study 1: Tables and Reservation

Is table number an attribute of ‘Reservation’?

Better modelled as a separate class:

tables exist even if there are no reservations;

other attributes of tables, e.g., size, can be stored.

CPSC-5360, Lesson 3

*

*

CPSC-5360, Lesson 3

*

Use of Constraints

Not all domain properties can be shown graphically:

e.g., it should be impossible to double-book a table.

Constraints add information to models:

written in a note connected to the model element being constrained.

CPSC-5360, Lesson 3

*

*

CPSC-5360, Lesson 3

*

Use of Generalization

A superclass can be used to show the properties shared by different types of booking.

CPSC-5360, Lesson 3

*

*

CPSC-5360, Lesson 3

*

Correctness

How do we know when a domain model is complete?

we do not: there are lots of plausible models in most cases.

Domain modelling is not an end in itself, but a guide to further development.

Realizing use cases tests the domain model, and will usually lead to refinements.

CPSC-5360, Lesson 3

*

*

CPSC-5360, Lesson 3

*

Supplementary Documents

  • Common Supplementary Documentation:
  • Glossary.
  • Activity Diagram.
  • Glossary:
  • A mini dictionary which captures concepts and vocabulary relevant in the problem domain.
  • Avoids misunderstanding and facilitates communication.
  • An Activity Diagram is an UML diagram that describes activities.

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

Case Study 1: Partial Glossary

Booking: an assignment of diners to a table.

Covers: the number of diners for a booking.

Customer: a person who makes a reservation.

Reservation: a booking made in advance.

Walk-in: a booking that is not made in advance.

CPSC-5360, Lesson 3

*

*

CPSC-5360, Lesson 3

*

Activity Diagrams

  • Similar to flow chart that describes sequence of activities.
  • Useful in:
  • Business Modelling (business workflow).
  • Use Cases (interrelation and interaction).
  • Design (algorithm, complex sequence etc).
  • Often associated with several classes.
  • One of the strengths of activity diagrams is the representation of concurrent activities.

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

Activity Diagrams (cont)

  • Diagram Elements:

Activity
Initial Node

Activity
End Node

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

Activity Diagrams (cont)

  • Action:
  • Fundamental block in an activity diagram.
  • Represents a unit of work (something is done).
  • Automatic transition upon completion.
  • Transition:
  • Represents the control flow: it is simply a movement between actions.
  • Initial and End Node:
  • Show the beginning and ending points in an activity diagram.

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

Case Study 1: Activity Diagram

  • Documenting the sequence when customer arrives.

  • Note the interrelation of Record Arrival and Record Walk-In.

CPSC-5360, Lesson 3

*

*

CPSC-5360, Lesson 3

*

Concurrent Actions

  • Independent actions which can be carried out at the same time (in parallel).
  • Shown using forks, joins and rendezvous:
  • Fork:
  • One incoming transition and multiple outgoing transitions.
  • Execution splits into multiple concurrent threads.
  • Rendezvous:
  • Multiple incoming and multiple outgoing transitions.
  • All incoming transitions must occur before the outgoing transitions.

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

Representing Concurrency

  • Join:
  • Multiple incoming transitions and one outgoing transition.
  • The outgoing transition will be taken when all incoming transitions have occurred.

CPSC-5360, Lesson 3

*

*

CPSC-5360, Lesson 3

*

Activity Diagram: Another Example

  • Use Cases:
  • Submit registration request.
  • Register student:
  • Verify prerequisites.
  • Verify course enrolment.
  • Verify special cases.

CPSC-5360, Lesson 3

*

*

CPSC-5360, Lesson 3

*

Swimlanes

  • Activity diagrams are most often associated with several classes:
  • The partition of activities among the existing classes can be explicitly shown using swimlanes.
  • Further clarify where an action takes place.

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

Swimlanes: Example

Verify

course not

full

Receive course

registration request

Check

prerequisites

Check

special

permission

Complete

registration

[ok]

[ok]

[ok]

[not ok]

[not ok]

[not ok]

Student

Course

Action taken by Student

Action taken by Course

CPSC-5360, Lesson 3

*

*

CPSC-5360, Lesson 3

*

Where are we now?

  • Typical Artifacts:
  • Requirement Specification.
  • Use Cases:
  • Use Case Description.
  • Use Case Diagrams.
  • Activity Diagrams.
  • Glossary.
  • Domain Model.

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

Summary

  • Introduction to Case Studies
  • Requirement Gathering
  • Use Case Modeling
  • Domain Modeling / Business Modeling
  • Activity Diagram

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

Reading suggestions

  • From [Priestley; 2004]
  • Chapter 4, sections 4.2 to 4.5
  • From [Wadhwa, Andrei, Soo; 2007]
  • Chapter 3
  • From [Larman; 2005]
  • Chapters 1, 6
  • From [Stevens, Pooley; 1999]
  • Chapter 11

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

Coming up next

  • Analysis:
  • [Priestley; 2004], Chapter 5
  • [Wadhwa, Andrei, Soo; 2007], Chapter 3
  • UML Class and Object Diagrams:
  • [Priestley; 2004], Chapter 8
  • [Wadhwa, Andrei, Soo; 2007], Chapter 4

CPSC-5360, Lesson 3

*

CPSC-5360, Lesson 3

*

Thank you for your attention!


Questions?

CPSC-5360, Lesson 3

*

*

*

*

*

*

*

*

Note: Intentionally left Incomplete

*

*

*

*

The ‘include’ dependency is inappropriate, because the interactions specified in ‘Record walk-in’ are not performed every time ‘Record arrival’ is performed.

Rather, ‘Record walk-in’ is performed in some cases of ‘Record Arrival’, when there is no booking for the customer, there is a suitable table free, and the customer still wants to eat there.

*

‘Record walk-in’ contains more details than ‘Record arrival’.

Rather, ‘Record walk-in’ is performed in some cases of ‘Record Arrival’, when there is no booking for the customer, there is a suitable table free, and the customer still wants to eat there.

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*