Table of Contents
0. Introduction The aim of this tutorial is to show how to use UML in "real" software development environment.
1. Elevator Problem
A product is to be installed to control elevators in a building with m floors. The problem concerns the logic required to move elevators between floors according to the following constraints:
- Each elevator has a set of m buttons, one for each floor. These illuminate when pressed and cause the elevator to visit the corresponding floor. The illumination is canceled when the elevator visits the corresponding floor.
- Each floor, except the first floor and top floor has two buttons, one to request and up-elevator and one to request a down-elevator. These buttons illuminate when pressed. The illumination is canceled when an elevator visits the floor and then moves in the desired direction.
- When an elevator has no requests, it remains at its current floor with its doors closed.
2. Unified Modeling Language UML is a modeling language that only specifies semantics and notation but no process is currently defined. Thus, we decided to do the analysis as follows;
- Use Case Diagram
- Class Diagram
- Sequence Diagram
- Collabration Diagram
- State Diagram
3. Analysis 3.1. Use case diagram
Use case description:
- A generalized description of how a system will be used.
- Provides an overview of the intended functionality of the system.
- Understandable by laymen as well as professionals.
Use Case Diagram:
Elevator basic scenario that can be extracted from Use Case Diagram:
- Passenger pressed floor button
- Elevator system detects floor button pressed
- Elevator moves to the floor
- Elevator doors open
- Passenger gets in and presses elevator button
- Elevator doors closes
- Elevator moves to required floor
- Elevator doors open
- Passenger gets out
- Elevator doors closes
3.2. Class Diagram
Class diagrams show the static structure of the object, their internal structure, and their relationships.
Class diagram:
3.3. State diagram
A state diagram shows the sequences of states an object goes through during it's life cycle in response to stimuli, together with its responses and actions.
4. Design
The design phase should produce the detailed class diagrams, collaboration diagrams, sequence diagrams, state diagrams, and activity diagram. However, the elevator problem is too simple for an activity diagram. Thus, we are not using an activity diagram for the elevator problem.
4.1. Sequence Diagram
A sequence diagram and collaboration diagram conveys similar information but expressed in different ways. A Sequence diagram shows the explicit sequence of messages suitable for modeling a real-time system, whereas a collobration diagram shows the relationships between objects.
Sequence Diagrams:
Sequence Diagram for Serving Elevator Button
Sequence Diagram for Serving Door Button
4.2. Collaboration diagram
- Describes the set of interactions between classes or types
- Shows the relationships among objects
Collabration diagrams:
Collabration Digaram for Serving Elevator Button 
Collabration Digaram for Serving Door Button
5. Detail Design
5.1. Detail Class Diagram
5.2. Detail Operation Description
Module Name Elevator_Control::Elevator_control_loop
Module Type Method
Input Argument None
Output Argument None
Error Message None
File Access None
File Change None
Method Invoke button::illuminate, button::cancel_illumination,
door::open, door::close, elevator::move, elevator::stop
Narative
5.3. Pseudo-Code
void elevator_control (void)
{
while a button has been pressed
if button not on
{
button::illuminate;
update request list;
}
else if elevator is moving up
{
if there is no request to stop at floor f
Elevator::move one floor up;
else
}
6. Acknowledgement
This example was developed for topic in software engineering in Vanderbilt University by myself and my best friends:
3 comments:
Really useful some one like me (newbea in design) but the diagrams are not visible.
Thanks Kalyan! Great Post! But the diagrams are not available.
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