What is real-time, really?
There’s a whole lot of talk about “real time” just now – from Google’s realtime search, to games, processing power, and medicine. And yet it strikes me that “realtime” (or is it real-time or real time?) is overused, and often meaningless.
Wikipedia defines realtime as “when things respond to events as they occur“. Well, I respond to events as they occur to me, but sometimes hours or days late… Dictionary.com defines it as “of or pertaining to applications in which the computer must respond as rapidly as required by the user or necessitated by the process being controlled.” Hm. Well – if the user required a response only the next day, would that still be realtime? Selecting “shutdown” on my PC shuts the PC down in about 5 minutes, which when I’ve walked away from the PC is as rapidly as required, but is hardly realtime.
It seems like the realtime I thought I knew is actually some concept which spans almost any sort of delay. My definition would be something much closer to “simultaneous” or “directly after”. In other words, within a short enough time-period that an average observer would say that the result/response happened right after the cause.
So if I click a mouse button to select something on screen, I expect that something to respond immediately.
And what is immediate? Well, as an example in tests of human reaction time (often by catching a falling ruler between finger tips), the average human reaction time tends to be in the range of 0.2 seconds, or 200 milliseconds. So it might be fair to say that anything that happens within that time period would be pretty immediate, or without perceptible delay.
So given that definition of realtime, what is ACTUALLY realtime?
- Twitter is mainly not as most updates are actually read out-of-sync
- SMS and email are mosty not, for the same reason
- Communicating by talking IS generally realtime
- Google’s search is barely realtime, if at all – it’s just very recent
- The feedback we get from machines can be realtime – from clicking on things, to turning the steering wheel, to turning on a light….
Actually, thinking through the options – there’s not much in life that is actually realtime…
