Figure 9. 28 : In some situations, devices may temporarily report conflicting
information about the state of the system. (Hand/phone by Siddarth Dasari,
thermometer by Saneef Ansari)
What can you do about this? You could fix this by making the controller check
in more frequently. But that would run the battery down within days. Users
don’t expect to have to change batteries in heating controllers several times a
week. So that’s not practical.
Your next option is to consider how you can design the smartphone UI to
account for this two minute period. There are two possible approaches.§
Firstly, you could show the updated settings the user wanted to apply: the
temperature setting of 21C, even though it might (for a short time) give a
misleading impression of th e system state. If the instruction cannot be applied
for some reason (e.g. temporary internet outage at the property), you can alert
the user and then revert the UI to the old state. In essence, you pretend that it
has worked while you wait for confirmation from the controller.
Instagram employ similar ‘white lies’ to make their mobile app feel more
responsive. For example, Instagram registers likes and comments in the app UI
while the request is still being sent to the service. The user is notified if the
action fails. They call this ‘performing actions optimistically’^18 (see figure
9.29).
(^18) Krieger, M ‘Secrets to Lightning-Fast Mobile Design’, Warm Gun conference 2011.
https://speakerdeck.com/mikeyk/secrets-to-lightning-fast-mobile-design