Clemson Transit Assistance System

 

The stakeholders in CTAS have a number of interests. The users of the system are interested in traveling to their destination and will use a system that makes that trip easier provided using the system is not too difficult. The governments of locales served by the system are interested in reducing traffic congestion and generally reducing the impact of travel on other area concerns. The providers of information to the system are interested in having their information accessible to as many travelers as possible as accurately as possible. Most of these providers are also interested in maximizing their revenue.

 

The actors in CTAS have a number of differing goals. The CTAS user wants to plan and execute a trip in the cheapest, fastest manner possible (Different users will have different priorities for these two).  Secondary Actors include information providers such as parking lots, transit systems, taxi companies, airlines, and map services. These actors want to attract business by providing fast response and accurate data. Information providers will change with locale and may change dynamically as they go offline outside their hours of operation. A CTAS device will have a core set of features that may be expanded by attaching the device to expansion devices. A CTAS device’s feature set will have the ability to adapt to a changing set of peripheral devices.

 

Actors

CTAS user – The user has a few routine destinations to which they will travel repeatedly from a usual origin, e.g. home to work. They need to be able to plan and revise trips on an ad hoc basis. They need easy to understand itineraries that reflect their familiarity with the itinerary.

 

CTAS information provider – Any actor that provides data to CTAS for use in computing itineraries. A vehicle in which the CTAS is being transported may provide time to destination information. A parking lot may provide its location and availability information.

 

CTAS smart unit – A special kind of information provider that is a building or transportation vehicle that provides information about itself such as a map or rules or help.

 

CTAS device – Any device on which an instance of CTAS may be hosted. This may be a dedicated device or a multi-purpose device such as a smartphone or PDA.

 

CTAS related hardware – An abstract secondary actor. Any piece of hardware that touches a CTAS device.

 

CTAS peripheral – A secondary actor that adds a specific capability to the CTAS device such as GPS capability. A certain set of preplanned peripherals are automatically recognized and the behavior of the system will adjust to the presence or absence of the peripheral. For example, when there is no GPS peripheral attached, the system asks the user for a location. 

 

CTAS expansion device – A secondary actor that provides a larger, more capable platform such as a vehicle or service port which can expand the CTAS device’s bandwidth range of output devices, etc.

 

Qualities

Using the ISO 9126 framework we specify the following qualities:

Functionality

Accurate – The itinerary produced by CTAS should be as accurate as the information provided to it. The system should fail visibly if the capacity of the system is exceeded rather than producing faulty results.

Interoperable – CTAS should be able to accept information from as many information providers as possible. Any standards should be identified and followed.

Secure – Communication between CTAS and information providers should be reasonably secure but since it is only the availability of resources, security is not a primary concern. Communication between CTAS and the user should be secure.

Reliability

Recoverable – Any itinerary should be persistent even in the event of spontaneous reboot of the system.

Usability

Understandability – The system should be understandable by persons with an 8th grade reading ability.

Learnability – The system should be learnable by a person capable of following the instructions for operating consumer electronic products.

Operability – The system should be operable by anyone capable of operating a telephone keypad.

Efficiency

Time behavior – CTAS should be able to produce an itinerary within 30 seconds of receiving the command.

Resource utilization – CTAS should be capable of operating in 256 M of dynamic memory.

Maintainability

Analyzability – A CTAS maintainer should be able to estimate the effort for a requested modification within 4 hours.

Changeability – A CATS maintainer should be able to accomplish most changes within 3 working days.

            Testability – CTAS should be moderately testable.

Portability

Adaptability – CTAS will be capable of being ported to a new device by replacing externally linkable drivers.

Installability – CTAS should be packaged using an automated installer usable by anyone meeting the usability requirements.

Replaceability – Upgrading CTAS should be possible using the same automation as for the initial installation.