Example 1: University   Government legislation may impact the overall mission of the University

and cause changes to strategic and tactical plans. Government funding may also impact these plans by applying constraints to the University's implementation plans. The User Community, of the University network, both internal and external, will influence strategic and tactical plans by making requests for hardware, software, or support. Private Sector Funding, to a lesser extent than Government funding, may also apply constraints on the strategic and tactical plans for the University. Industry, both inside and outside the province, will influence the strategic and tactical plans for the University by making requests to the University for services and setting new educational requirements for University programs. The Education Community is made up of universities, public schools, vocational schools, private educational institutions, and university educators. This group will influence the strategic and tactical plans for the University in many ways, for example, by making requests for educational services, gaining a competitive advantage through technology, or gaining advancement in educational techniques.

Example 1: University   Government legislation may impact the overall mission of the University

and cause changes to strategic and tactical plans. Government funding may also impact these plans by applying constraints to the University's implementation plans. The User Community, of the University network, both internal and external, will influence strategic and tactical plans by making requests for hardware, software, or support. Private Sector Funding, to a lesser extent than Government funding, may also apply constraints on the strategic and tactical plans for the University. Industry, both inside and outside the province, will influence the strategic and tactical plans for the University by making requests to the University for services and setting new educational requirements for University programs. The Education Community is made up of universities, public schools, vocational schools, private educational institutions, and university educators. This group will influence the strategic and tactical plans for the University in many ways, for example, by making requests for educational services, gaining a competitive advantage through technology, or gaining advancement in educational techniques.

Example 1: University Context Diagram

Example 2: 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 homeowner through a keypad and function keys contained in the SafeHome control panel.During installation, the SafeHome control 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 number(s) are input for dialing when a sensor event occurs.When a sensor event is recognized, the software invokes an audible alarm attached to the system. After a delay time that is specified by the homeowner 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 redialed every 20 seconds until telephone connection is obtained.All interaction with SafeHome is managed by a user-interaction subsystem that reads input provided through the keypad and function keys, displays prompting messages on the LCD display, displays system status information on the LCD display. Keyboard interaction takes the following form ...

Example 2: 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 homeowner through a keypad and function keys contained in the SafeHome control panel. During installation, the SafeHome control 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 number(s) are input for dialing when a sensor event occurs. When a sensor event is recognized, the software invokes an audible alarm attached to the system. After a delay time that is specified by the homeowner 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 redialed every 20 seconds until telephone connection is obtained. All interaction with SafeHome is managed by a user-interaction subsystem that reads input provided through the keypad and function keys, displays prompting messages on the LCD display, displays system status information on the LCD display.

Example 2: SafeHome Context Diagram

Example 2: Level 0 DFD

Example 2: 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 homeowner through a keypad and function keys contained in the SafeHome control panel. During installation, the SafeHome control 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 number(s) are input for dialing when a sensor event occurs. When a sensor event is recognized, the software invokes an audible alarm attached to the system. After a delay time that is specified by the homeowner 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 redialed every 20 seconds until telephone connection is obtained. All interaction with SafeHome is managed by a user-interaction subsystem that reads input provided through the keypad and function keys, displays prompting messages on the LCD display, displays system status information on the LCD display. Keyboard interaction takes the following form ...

Example 2: Level 1 DFD

Rules for Data Flow Diagramming   Process:

  No process can have only outputs   No process can have only outputs.   A process has a verb-phrase label (sound familiar)

  Data Store:   Data cannot move directly from one data store to

another. It must flow through a process.   Data cannot be moved directly from an outside data

source or sink to a data store. It must first go through a process.

  A data store has a noun-phrase label.   Source / Sink:

  Data cannot move directly from a source to a sink. It must be moved by a process.

  A source/sink has a noun-phrase label.

Rules for Data Flow Diagramming (cont’d)   Data Flow:

  A data flow has only one direction of flows between symbols. This is called a net flow: Example: a read before an update will show one arrow for the update only.

  A fork in a data flow means a copy of the data is going to more than one location.

  A join in a data flow (not shown) means data is being received from more than one process, data store and/or data sink/source.

  A data flow cannot loop back to itself. If it does need to loop back, it must flow through a process.

  A data flow to a data store means an update (delete or change).

  A data flow from a data store implies a read. A data flow has a noun-phrase label.

Example2: Level 2 DFD for Monitor Sensors Process

Example 3: ATM

 Using your knowledge of how an ATM is used, develop a set of use cases that could serve as a basis for understanding the requirements for an ATM system.

Example 3: Withdraw cash   Actors: Customer, ATM, Accounting system   Inputs: Customer’s card, PIN, Bank Account details   Outputs: Customer’s card, Receipt, Bank account details   Normal operation: The customer inputs his/her card into the

machine. He/she is promoted for a PIN which is entered on the keypad. If correct, he/she is presented with a menu of options. The Withdraw cash option is selected. The customer is promoted with a request for the amount of cash required and inputs the amount. If there are sufficient funds in his/her account, the cash is dispensed, a receipt if printed and the account balance is updated. Before the cash is dispensed, the card is returned to the customer who is prompted by the machine to take their card.

  Exception:   Invalid card. Card is retained by machine; Customer advised to seek advice.   Incorrect PIN. Customer is request to rekey PIN. If incorrect after 3 attempts,

card is retained by machine and customer advised to seek advice.   Insufficient balance. Transaction terminated. Card returned to customer.

Example 3: Display balance   Actors: Customer, ATM, Accounting system   Inputs: Customer’s card, PIN, Bank Account

details   Outputs: Customer’s card   Normal operation: The customer authenticates

using card and PIN as in Withdraw cash and selects the Display Balance option. The current balance of their account is displayed on the screen. The card is returned to the customer.

  Exception:   Invalid card. As in Withdraw cash   Incorrect PIN. As in Withdraw cash

Example 3: Print statement   Actors: Customer, ATM, Accounting system   Inputs: Customer’s card, PIN, Bank Account

details   Outputs: Customer’s card, Printed statement   Normal operation: The customer authenticates

using card and PIN as in Withdraw cash and selects the Print statement option. The last five transactions on their account is printed. The card is returned to the customer.

  Exception:   Invalid card. As in Withdraw cash   Incorrect PIN. As in Withdraw cash

Example 3: Change PIN   Actors: Customer, ATM   Inputs: Customer’s card, PIN   Outputs: Customer’s card   Normal operation: The customer authenticates as

in Withdraw cash and selects the Change PIN option. He/she is prompted twice to input the new PIN. The PINs input should be the same. The customer’s PIN is encrypted and stored on the card. Card returned to customer.

  Exception:   Invalid card. As in Withdraw cash.   Incorrect PIN. As in Withdraw cash.   PINS do not match. The customer is invited to repeat the

process to reset his/her PIN.

Example 3: Deposit cash   Actors: Customer, ATM, Accounting system   Inputs: Customer’s card, PIN, Bank Account details, Cash to be

deposited   Outputs: Customer’s card, Receipt   Normal operation: The customer authenticates as in Withdraw cash

and selects the Deposit option. The customer is promoted with a request for the amount of cash to be deposited and inputs the amount. He or she is then issued with a deposit envelope in which they should put the cash then return it to the machine. The customer’s account balance is updated with the amount deposited but this is marked as uncleared funds and is not cleared until checked. A receipt is issued and the customer’s card is returned.

  Exception:   Invalid card. As in Withdraw cash.   Incorrect PIN. As in Withdraw cash.   No cash deposited within 1 minute of envelope being issued. Transaction

terminated. Card returned to customer.