Single Cabin Elevator Control System
Use Case: Take Lift
Date: 30 May, 2001; Author: Shane Sendall (LGL-DI-EPFL)
Single Cabin Elevator Control System
Use Case: Take Lift
Scope: Elevator Control System
Level: User Goal
Intention in Context: The User intents to go from one floor to another. The System has a single lift cabin that may service many users at any one time.
Primary Actor: User
Main Success Scenario:
1. User requests System for lift from a particular floor, also indicating the direction desired.
2. System acknowledges User's request and commands the lift to pick up User.
3. System ascertains that lift has reached User's floor+; it commands lift to stop and open its Door, and informs User.
4. User enters lift and requests System to go to a floor as destination.
5. System acknowledges User's request.
6. Door informs System of closure; System commands lift to go to destination floor.
7. System ascertains that lift has reached destination floor+; it commands lift to stop and open its Door, and informs User.
8. User exits lift.
Extensions:
2a. System determines that the lift is available at the User's floor with door open:
2a.1. System requests the Door to stay open; use case continues at step 4.
2b. System determines that the lift is available at the User's floor with door closed:
2b.1. System commands lift to open its Door; use case continues at step 4.
2c. System ascertains that the lift is currently unavailable:
2c.1. System acknowledges User's request.
2c.2. System ascertains that the lift has reached User's floor+:
2c.3. System commands lift to stop and open its Door, and informs User; use case continues at step 4.
(4-7)||a. User requests System to go to a number of additional floors*:
(4-7)||a.1. System acknowledges each additional request of User; use case continues from where it was interrupted.
4a. User does not make a request (or took the stairs)**:
4a.1. Door informs System of closure; use case ends in failure.
4b. Door informs System of closure++:
4b.1. User requests System to go to a floor as destination.
4b.2. System acknowledges User's request, and commands lift to go to destination floor; use case continues at step 7.
5a. System determines that lift is already at destination floor:
5a.1. System commands lift to open its Door, and informs User; use case continues at step 8.
8a. System determines that there are additional requests pending*: use case continues at step 6.
Notes:
* System cannot make difference between a single User making a number of requests and many Users each making a request
** undetectable by system
+ Floor Sensor indicates each floor that is reached
++ User has already entered lift (undetectable by system)