System Specification

Contents:

Send questions to: thwang@cs.stanford.edu

Last updated:
December 10, 1998

7.0 System Specification:

The main focus of our prototype is the integration of a food-ordering system at the gas pump display. The following paragraphs will concentrate on how a customer orders food via the new interface. There are various tools and languages to specify how humans (customers) and machines (the gas pump display) interact with each other.

One of the most popular tools to accomplish this kind of task is “UAN” (User Action Notation). An in-depth look reveals, however, that the glossary of UAN is more related to computer devices than anything else. Common words in UAN include click, release mouse button, select files and etc, whereas our prototype is primarily a touch screen and our main objects are nothing but the numerical keypad and the food menus. The UAN does not readily provide the vocabulary and syntax to describe our prototype.

Due to the deficiency stated earlier, we switched to other three tools, namely “ Structured English”, “ Backus Naur Form” and “State Transition Diagram”, to complete our system specification.

7.1 Structured English:

Task: Ordering food at the gas pump display

Repeat WHILE users do not make choices
     Display “Taco Bell” logo
     Toggle the Taco Bell logo with the main food menu
     Keep on displaying the message “ Want some…”
If “YES” is selected
     Repeat WHILE the “DONE” button is NOT pressed
User touch the food menu item to select
     Items ordered are displayed in the right column as “E-receipt”
          Left to each item in “E-receipt”, “remove” button is displayed
          When “DONE” button is clicked
               The total food price is displayed
               The order is sent to the kitchen
               A receipt is printed out
               The screen redisplays the Taco Bell logo
Otherwise
     Keep on displaying the food menus until gas pumping is done
     Print the regular receipt and prompt the users to take it

7.2 Backus Naur Form:
H: the gas station customers G: the new gas pump display

Display::=G:Taco Bell logo | H:User selection
User selection::=H:Meal deals | H:Items
Meal deals::=<H:Meal deals><H:Items><E-receipt>|<H:Food order>
Items::=<H:Items><H:Meal deals><E-receipt>|<H:Food order>
Food order::=<G:Order number><H:Pickup>

7.3 State Transition Diagram: