1998 - Draper Laboratory

APPENDIX 2:User InterfaceRequirementsfor Testers and DevelopersWhile the specific implementation of user interfaces can quicklytransform into personal preference battles, our approach is to list some ofthe key interface requirements that these two diverse user groups require.In general, testers and developers require methods for scripting events.Event starting times should allow for the following options: absoluteGPS times, relative GPS time into a scenario, and time to the nearest GPSbit position boundary in the navigation message (subframe and page orabsolute bit position).While testers will generally be satisfied with a priori scripting of theentire test, developers will require the ability to change the scenario as itis running. However, the developer’s user interface should not requirehim to tediously enter hundreds of keystrokes in real time for eachdesired change. Instead, developers will appreciate an option for storingaway favorite changes in files, and at appropriate moments, invokingsmall subscripts or macros that effectively fill in all of the menu optionsneeded. As long as the developer submits the desired changes withenough lead time for the scenario processing computer to make thechanges, it should be possible to compute the new changes. Becauseoperating systems such as Windows NT, DEC VMS, VxWorks, Micro-Tek/VRTX, and selected variants of UNIX have true multiprocessing andreal-time operation, it should be possible for a user to open up a newsession as the simulator is running, use an editor to create a macro ormini-script, save that macro in a file, and then submit the desiredchanges to the simulator scenario processor.Validating the Validating Tool: Defining and Measuring GPS Simulator Specifications15