Response Time Requirements
A
response time requirement is a
performance
requirement that specifies a maximum amount of the
performance
quality subfactor
response time.
The typical objectives of a response time requirement are
to:
- Ensure that the application or component does not make a
user wonder whether or not it has received the user’s
request.
- Ensure that the application or component deals with
time-critical inputs before their information is
obsolete.
Response time requirements are typically specified in terms
of the following measurements:
- Maximum time delay.
- Maximum average time delay.
The following are typical examples of response time
requirements:
- “The application shall clearly acknowledge all user
requests within 0.5 seconds.”
- “The application shall store the stock market feed
faster than it is received so that no information is
lost.”
The following guidelines have been found to be useful when
producing response time requirements:
- The scope of a response time requirement can be:
- Response time requirements can address the time taken to
respond to client applications as well as human actors.
- A tight latency response requirement implies an even
tighter response time requirement.
- Response time requirements are often implemented by
displaying a constantly changing percent complete status bar,
a hourglass, and a change in button appearance when the
complete transaction results in a long latency period (e.g.,
an interaction involving large amounts of processing and
database access over a low bandwidth network).
For example, the application might display an hourglass
on the user’s screen while waiting for a complex data
query to return, be properly formatted, and displayed.