Forget the marketing-speak, curious to see what formal definitions are used. Are these typically system response latency cutoffs that vary by industry? ie. 1 second would not be real-time for algo trading, but might be for tweet aggregation for brands
If we speak about human interactions, I think that it should be less than 250ms.
In 1968 Robert Miller published his classic paper Response time in man-computer conversational transactions in which he described three different orders of magnitude of computer mainframe responsiveness:
- A response time of 100ms is perceived as instantaneous.
- Response times of 1 second or less are fast enough for users to feel they are interacting freely with the information.
- Response times greater than 10 seconds completely lose the user’s attention.
But I totally agree with you, it totally depends on what is the purpose of your system.
My relatively non-formally informed opinion is that one property that seems to correlate with real time is:
R ≤ S
Where R is the maximum time it takes to return a useful result and S is the maximum sample rate. Anything else suggests that results queue up and hence the time to return a result varies.
In 1968 Robert Miller published his classic paper Response time in man-computer conversational transactions in which he described three different orders of magnitude of computer mainframe responsiveness:
- A response time of 100ms is perceived as instantaneous.
- Response times of 1 second or less are fast enough for users to feel they are interacting freely with the information.
- Response times greater than 10 seconds completely lose the user’s attention.
But I totally agree with you, it totally depends on what is the purpose of your system.