Microsoft is grappling with the usability requirements of Avalon. I feel it is important to quantify the “perceived performance” or response times of all applications. I've often heard the term “90% of transactions in under 2 seconds” for distributed applications. I haven't seen any formal metrics on that, but there is a formal metric to define the following terms for responsiveness:
- Immediate. 0.1 seconds
- Uninterrupted. 1.0 seconds
- Focused. 10 seconds
- Delayed. > 10 seconds
Jakob Nielsen, author of Usability Engineering, talks about these agreed upon metrics. It would be good for a requirements team to used these defined terms so that responsiveness of the application can be measured against requirements. Since I worked on the NeXT system in '89, I've always dreamed of creating a command wrapper that automatically moved through the wait cursor and progress bar window for all commands.