GEORGE MASON UNIVERSITY
DEPARTMENT OF INFORMATION &
SOFTWARE ENGINEERING
SWE 721 / IT 821 - Reusable Software Architectures
Automated Highway System Software Product Line
Spring 2007
Problem Definition:
There are automated highway toll systems
deployed in various states throughout the
Customers wishing to use automated transponders purchase these transponders through the regional toll center. This regional center maintains customer accounts in a database including owner and vehicle information, account balance, and history. Customer purchasing a transponder must pay ahead for toll fees by credit card. Customers are notified by email or postal mail when the accounts are running low and if the account is out of funds. Some toll systems have toll booths equipped with a traffic light and alarm to indicate whether the vehicle has been authorized to pass through the toll booth. The traffic light turns yellow when the account is low on funds. Accounts are reduced by the toll amount incurred at the end of each trip. In some automated highway systems, the toll amount to be paid depends on the length of the trip and category of the vehicle.
For access onto the toll highway, toll systems can have several kinds of entry toll booths:
1. All toll systems contain Transponder only entry toll booths with no barrier.
2. Some toll sytems contain a Ticket issuing entry toll booth with barrier. The driver presses a button to receive the ticket.
To leave the toll highway, there are several kinds of exit toll booths:
1. All toll systems contain Transponder only exit booths with no barrier.
2. Some toll systems contain a Ticket reading exit toll booth with barrier. The ticket reading booth contains a ticket reader, a coin/cash reader, and a credit card reader that can be used by the driver.
3. Some toll systems contain a Human operated full service booth with barrier. A teller at the full service booth accepts cash or credit card payments using a cash register and credit card reader connected to a computer at the toll booth.
All toll systems contain toll booths that have an operational light to indicate whether the toll booth is available for use; a vehicle-approaching sensor (placed 50 feet in front of the toll booth); a vehicle-passed sensor; a transponder sensor which can read and write to the transponder; and a camera. Additionally, all toll booths other than the high-speed / transponder-only lanes contain a vehicle barrier that is raised and lowered to enforce payment.
Some automated highway systems equip toll booths with a traffic light and an alarm. This traffic light is initially red and, if present, the barrier is lowered. When a vehicle approaches the toll booth, the vehicle sensor detects the vehicle’s presence. If this is a transponder-only booth, the transponder sensor detects a valid transponder in the approaching vehicle, and the system switches the traffic light to green. If this is not a transponder-only booth, the system waits for an action from the driver or operator. In the case of a successful payment, the light will be turned to green and the barrier will be raised. The traffic light is returned to red and the barrier lowered after the car passes. If a vehicle passes through the toll booth while the traffic light is still red, an alarm sounds, the video camera photographs the license plate, and the image is sent to the local police liaison office.
Ticket-reading exit toll booths have a card reader device, which can read both toll booth issued tickets and credit cards. Ticket-reading exit toll booths that allow payment by cash have a coin/cash reader device that accepts exact change. Finally, full service exit toll booths do not have card and coin/cash readers that can be used by the driver, but have an operator who collects the appropriate toll and authorizes a car to pass. After the driver inserts the ticket into the card reader, the entry point and toll amount (which are read off the ticket) will be displayed on the operator’s display.
Not all automated highway systems require the use of a transponder in the high-speed transponder only toll booths. In some toll systems, entering and exiting through a transponder-only booth without a transponder is prohibited and results in a violation; in some other toll systems entering and exiting through a transponder-only booth without a transponder is allowed, but results in a higher toll.
The toll calculation also varies by toll system. In some toll systems, the toll is calculated based on variables such as the time of day, the vehicle type, and the distance traveled. In some other toll systems, the customer pays a flat fee for using specific toll booth plazas.
In the future, automated highway systems may be installed into other states and possibly in other countries. These systems share many similarities but have some variations, such as the speed limit with which vehicles may pass through, the types of transponder devices supported, and how the toll amount is calculated. An automated highway system software product line will aid the development and configuration of these systems.
Requirements modeling
task:
Your task is to do a
commonality/variability analysis on the toll
booth clients and server of the problem definition for an automated highway
toll system, and come up with a feature model, context model, use case model,
and feature to use case relationship table for an
a. A product line context model depicted on a context diagram showing how the product line interfaces to the external environment
b. A use case model, consisting of a description of the actors and the use cases, including kernel, optional and alternative use cases, and use case variation points, which fully define the product line. Describe each use case in terms of the actors and their interactions with the system.
c. A feature model identifying the reusable capabilities of the product line. Describe and classify the features using a glossary, and draw a feature model showing all features and feature relationships.
d. A description of feature to use case relationships, shown as a table similar to table 5.1 in p. 109 of the course textbook.
e. A glossary briefly defining the features
2) Analysis Modeling
a.
Develop a static model using
class diagrams for the entity classes in the product line, then determine the
attributes of the classes, and the relationships between them.
b.
Develop interaction diagrams
(using either communication diagrams or sequence diagrams) for each kernel,
optional and variant use case. Identify the object structuring criteria used.
Document briefly the message sequence descriptions.
c.
Develop a statechart showing the different states of a toll booth.
Make sure that the statechart is consistent with the
appropriate interaction diagram(s).
d.
Develop a feature/class
dependency model showing the features, as well as their relationships to
optional and variant classes.
3) Design
modeling (Architectural Design Specification)
a.
An integrated set of
communication diagrams showing subsystems and objects, as well as the message
interfaces.
b.
A Distributed Software
Architecture document describing how the product line is decomposed into
component-based subsystems and the message interfaces between the subsystems
(depicted on a concurrent communication diagram). It should also explain how
the subsystems were determined.
c.
A component based software
architecture showing the components and connectors, including ports and
interfaces.
Glossary
Automated highway system: A collection of toll roads in a particular region that is managed by an agency responsible for the account administration of the toll road users.
Toll road: A road with a fixed number of toll plazas, at a number of locations in the road.
Toll plaza: a collection of entry and exit toll booths at one location in a toll road.
Toll booth: A point of entry or exit for a vehicle at a toll plaza.
Transponder: A device (tag) that is attached to the interior or exterior of a vehicle that can store information about its id, and entry and exit locations.
Transponder scanner: An antenna located above the roadway which can read and write information to and from a transponder.
Appendix
The following references can be looked at to see the types of features that are present in existing toll systems.
EZ-Pass is an automated highway
system based in
In