M'Sc Computing Science Software Engineering Lecture 8

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M.Sc Computing Science Software Engineering
Lecture 8

• Eli Katsiri
• Department of Computer Science
• and Information Systems
• Birkbeck College, University of London
• Email eli_at_dcs.bbk.ac.uk
• Web Page http//www.dcs.bbk.ac.uk/eli

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Summary of Lecture 7

• Video Rental use-case
• Centralised architecture
• De-centralised architecture
• comparison

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Centralised approach
4
De-centralised approach
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Outline of Lecture 8

• SafeHome system
• Panel diagram (UI)
• Descriptive narrative about the overall
  functionality (requirements)
• Home owner interacts use-case.
• Home owner system activation use-case.
• Coursework presentation

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SafeHome panel
away
off
stay
SAFEHOME
away stay instant bypass not ready
01 alarm check fire
1
3
2
bypass
test
max
4
5
6
chime
code
instant
7
8
9
ready
armed
power

0

panic
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SafeHome

• Safehome software enables the homeowner to
  configure the security system when it is
  installed, monitors all sensors connected to the
  security system and interacts with the home owner
  through a keypad and function keys contained in
  the SafeHome control panel.
• During installation the SafeHome panel is used to
  program and configure the system. Each sensor
  is assigned a number and type, a master password
  is programmed for arming and disarming the system
  and telephone numbers are input for dialing when
  a sensor event occurs.
• When a sensor event is recognised the sensor
  invokes an audible alarm attached to the system.
  After a delay time that is specified by the home
  owner during system configuration activities the
  software dials a telephone number of a monitoring
  service, provides information about the location,
  reporting the nature of the event that has been
  detected. The telephone number will be redialled
  every 20 secs until telephone connection is
  obtained.
• All interaction with SafeHome is managed by a
  user-interaction subsystem that reads input
  provided through the keypad function keys,
  displays prompting messages on the LCD display,
  displays system status information on the LCD
  display.

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Actors

• Homeowner
• Sensors
• Monitoring service

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Homeowner

• A homeowner interacts with the system in the
  following ways
• Enters a password to allow all other interactions
• Inquires about the status of a security zone
• Inquires about the status of a sensor
• Presses the panic button in an emergency
• Activates/deactivates the security alarm

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SafeHome Use Case Diagram (A)
interacts
configures
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SafeHome Use Case Diagram (B)
Validates password
Enters password
ltltusesgtgt
ltltusesgtgt
Inquires zone status
Query sensor
ltltusesgtgt
Inquires sensor status
Presses panic button
Activates/ deactivates system
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System activation use-case

• The homeowner observes a prototype of the
  SafeHome control panel to determine if the
  system is ready for input. If the system is not
  ready, the homeowner must physically close
  windows/doors so that the ready indicator is
  present. A not ready indicator implies that a
  sensor is open, i.e. that a door or window is
  open.
• The homeowner uses the keypad to key-in a four
  digit password. The password is compared with the
  valid password stored in the system. If the
  password is incorrect, the control panel will
  beep once and reset itself for additional input.
  If the password is correct, the control panel
  awaits further action.
• The homeowner selects and keys in stay or away to
  activate the system. Stay activates only
  perimeter sensors (inside motion detecting
  sensors are deactivated). Away activates all
  sensors.
• When activation occurs, a red alarm light can be
  observed by the homeowner.

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Noun lists
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6 selection criteria

• Retained information
• Information about a class needs to be remembered
  so that the system can function.
• Needed services
• Must have a set of identifiable operations that
  can change the value of its attributes in some
  way.
• Multiple attributes
• Major information. More than one attributes.
• Common attributes
• Attributes apply to all occurrences of the
  object.
• Common operations
• Operations apply to all occurrences of the
  object.
• Essential requirements
• External entities that appear in the problem
  space and produce or consume information.

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Noun lists
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Polymorphism
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Composition
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Domain Model
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CDC
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Coursework Art Gallery

• Software Engineering
• M.Sc Computing Science
• Department of Computer Science
• and Information Systems
• Birkbeck College, University of London
• Wednesday, 27 February 2008
• Deadline 17 April 2008
• Penalty for delay Grade Grade 5
  DaysOfDelay

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coursework

• An art gallery exhibits paintings and sculptures.
  Both are linked to displacement sensors which are
  triggered if the objects are moved. All exhibits
  are shown in rooms and every room has one or
  several motion sensors, which can also be
  triggered. Each room has an alarm, which is
  notified when either motion or displacement
  sensors are triggered. The alarm is connected to
  a central security system, to which all alarms
  are notified. The security system must create an
  alarm report containing the room number in which
  the alarm occurred and a description of the
  exhibits that are affected and must append this
  report to a log. When a displacement sensor is
  triggered, only the related exhibit is considered
  to be affected. When a room motion sensor is
  triggered, all exhibits in that room are
  considered to be affected. Once notified the
  security system can then identify the closest
  guard to the scene of the incident and page her.
  It is assumed that all objects representing
  security guards have an attribute indicating the
  guards current location, which is updated by an
  external location service.

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Task 1

• Design a domain model that includes the
  conceptual objects derived from the descriptive
  narrative.
• In no more than 20 lines comment on your design
  and discuss any alternatives.

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Task 2

• Draw a class diagram of the systems
  architecture. Indicate the nature and cardinality
  of all relationships, any abstract classes and
  indicate which attributes and methods you would
  expect each object to provide.
• Discuss your design in no more than 20 lines
  showing what decisions you have made to reduce
  coupling and increase cohesion.

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Task 3

• Give a collaboration diagram indicating the
  invocations occurring when a sensor connected to
  a painting is triggered. Indicate sequence
  numbers.
• Give a sequence diagram indicating the
  invocations occurring when a motion sensor
  included in a room is triggered. Indicate the
  signature of each operation invocation, i.e the
  name and type of input arguments and name and
  type of the objects that are returned.

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Task 4

• Map 3 classes to implementation. For each class,
  write class definitions (attributes and method
  signatures) and method definitions based on the
  interaction and design class diagrams .
• Hint It is not required to create fully-working
  code. In the method bodies you should only
  include statements that denote the order in which
  messages are sent (methods are invoked) in the
  interaction diagrams.

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Remarks

• Comments that will strengthen your work
• Try to justify and comment on analysis and design
  decisions. Discuss informally what led you to
  analyze and design part of the system in a
  specific manner.
• Describe briefly the methodology used to perform
  a task, based on the output of previous tasks.
  For instance, mention a few points about how one
  can derive different parts of the Implementation
  Model based on Interaction Diagrams or DCDs.
• Use Rational Rose, MSStudio2008, Eclipse, UMLET
  or another similar tool that you are familiar
  with for all tasks.