6 ms·

It Isn’t Your Father’s Realtime Anymore: The Misuse of a Noble Term (2006)

49 points by matt_d 11y ago

nickpsecurity 11y ago
I think I have a pretty straight-forward answer to his question about its popularity: real-time became synonymous with instant results and zero delays to mainstream audiences. Not sure exactly from what sources but that's the common denominator across all of these usages.
- bbrazil 11y ago
  I think it's devolved beyond that into a marketing term, I've seen realtime mean anything from milliseconds to hours. I'd mostly interpret it as "faster than what you already have/are used to".
  - TeMPOraL 11y ago
    I'd argue that GP is right, but only partially. It may be true that "real-time became synonymous with instant results and zero delays to mainstream audiences". But the story continues: then the sales&marketing folks and various other bullshitters noticed that "realtime = fast" and "fast = good", and they did what they always do - stared to stretch the term so that they can steal some of the good feelings associated with it, even though their products don't deserve them. It's what happened with the word "hacker", or is happening with the word "geek" right now. If something is associated with good qualities among relevant enough audience, it will be co-opted by marketing and then used and abused until it loses any meaning. That's what I hate about sales&marketing - it will fuck up everything that's cool. And journalism, I guess is to blame too (they are marketers too, competing for our attention). My pet peeve: ever heard about a company "going nuclear" or taking "a nuclear option"? That phrase should not be used to mean anything less serious than threatening to deploy an actual ICBM.
    - nickpsecurity 11y ago
      Your addition to my theory is probably right. I left it off just because I can't trace the specifics. Marketing and media are where I'd point the finger, though.
  - detaro 11y ago
    I'd say that real-time covering hours is less a marketing artifact but part of the academic definition that real-time means that guaranteed timing limits are kept, whatever size they have.
  - derefr 11y ago
    From the business analytics example, I think a useful layman's definition of "realtime" might be able to be extracted: "fast enough that, given the speed of the task the client is trying to accomplish, the client is never blocked waiting on the computation in such a way that it then performs suboptinally against its deadlines." In machine-assisted translation, "realtime" is whatever speed (milliseconds) is fast enough to have a conversation without pausing. In business, "realtime" is whatever speed (minutes/hours) is fast enough that the feed of information outpaces your ability to absorb and change strategy in response to the information. Interestingly, VR technology is "realtime" by both definitions: any perceptible latency (layman's definition) is unacceptable and causes feelings of "VR sickness"—so hard limits on frame delivery (technical definition) must be set. Or, "VR must be hard realtime in order to be realtime."
    - nickpsecurity 11y ago
      "I think a useful layman's definition of "realtime" might be able to be extracted: "fast enough that, given the speed of the task the client is trying to accomplish, the client is never blocked waiting on the computation in such a way that it then performs suboptinally against its deadlines."" That's actually a reasonable definition that could lead to re-interpretation and new usage by lay people. VR is a good example. Matter of fact, we did use that in game design because we had to differentiate between what had no delay and the pre-rendered graphics used in cut-scenes. We normally just said gameplay footage but some said "rendered in real-time." Those using VRML (the "VWWW") on dial-up knew what the opposite of real-time was. ;)
  - rocky1138 11y ago
    I remember it really annoying me when I was in high school and I would see a minivan drive past that had "real time AWD." I think it was a Mazda, but I can't be sure. As though without it there would be some sort of batch processing delay when driving the car...?
    - nickpsecurity 11y ago
      Even the Flintstones didn't have to batch it all the way. Wonder who Mazda's real competition is?
- VLM 11y ago
  Real time used to be extremely difficult, therefore it was extremely well designed and engineered. Think of the engineering and quality level of a stereotypical multi-million dollar industrial machine with hard real time nanosecond level response. Jitter in the response rate can be measured and correlated with tool lifetime and product scrap rates, for example. Think like a PR guy, use some empathy: Isn't complicated well engineered high quality stuff cool and easy to sell? I know, we'll call our Angry Birds tablet "real time". After all if "real time" is a phrase that sells five axis milling machine motor control systems, think how well it'll sell thermostats? Sure the engineers will be pissed off at the bastardization of their technical term but I'm paid on commission so who cares what they think... if they complain I'll call them "hackers" again to shut them up, that usually works pretty well. Look how in mass media, "quantum" usually passes for the opposite of the technical physics definition. There is an inherent danger where theres a profit motive in divide and conqueor style separation of people, the makers vs the consumers could eventually become as bad as the UK vs US two cultures separated by a common language.
richmarr 11y ago
This title is literally true for me. During the 70s my dad & his team built a programming language & runtime environment for realtime control systems in power stations. It was called Cutlass, and it's still in (dwindling) use today. In my dad's context, the term 'realtime' drew the most useful distinction between types of system in that context. In the web days, the term is used slightly differently, but still draws broadly the most useful distinction within the context. And lastly in media, the tech industry and computer subcultures have a pretty bad track record of protecting words from mis-use... troll, hacker, repo, pull-request, etc. all have comically uninformed usage. You don't quarrel with folk who buy ink by the barrel, nor do you get far telling them that they're doing language wrong. Personally this isn't an issue I choose to care about, language is contextual after all, but even if you do my advice would be to save your blood pressure for a fight you have a hope of winning.
dwc 11y ago
Devolution/devaluation seems very common now. I'm not sure if it's my perspective or if it's really worse that it used to be. Some examples: * ROM: something you download and install on your Android phone (as opposed to socketing a new chip) * Machine Learning: any change in program behavior based on feedback input (we used to call this programming) * Disruptive: doing business at least slightly different than someone else (as opposed to a new paradigm that sends shockwaves through a whole industry) * Fork: make a copy of a project (as opposed to starting a rival project based on the codebase of another project)
- oldmanjay 11y ago
  Considering any of that "worse" is definitely your perspective. It's simple back-in-my-day-ism to apply a value judgment to language use.
  - anon4 11y ago
    I used to be with "it". Then they redefined what "it" was and it wasn't what I was with. Now I can't be with what I used to be, because it's "it", but "it" is now different. In other words, embrace, extend, extinguish.
  - UmDieWelt 11y ago
    The point is that the words don't really have a useful meaning anymore. It is especially important in technical topics to have terms with some specific meaning.
    - Retra 11y ago
      It's important to be able to construct specific meanings. You don't need terms to do that, and you run a major communication risk by relying on terms that you aren't willing to define. And if you define them first, then you can use them however you like.
      - kuschku 11y ago
luckydude 11y ago
I blame all the misguided folks who try and add "soft real time" to time sharing systems like Unix/Linux/etc. Anyone who does that has a profound misunderstanding of what real time is, it most definitely is not a time sharing system. If you want a time sharing system and real time, that problem has been solved, in a really elegant way. Victor Yodaiken did it years ago, he made a small real time kernel and he ran all of Linux as the idle process in the real time kernel. When Linux thought it was disabling interrupts it wasn't, only the real time kernel could do that. He had a demo where he was running xperf (or some fairly compute intensive X thing) while running tar cf - / | rsh someotherhost 'cat > /dev/null' while the real time kernel was gathering events. He never missed a deadline or dropped an event. Sweetest design I've ever seen, have your cake and eat it too.
- AnthonyMouse 11y ago
  > I blame all the misguided folks who try and add "soft real time" to time sharing systems like Unix/Linux/etc. Anyone who does that has a profound misunderstanding of what real time is, it most definitely is not a time sharing system. Part of the problem is that there are realtime systems where, if you don't meet the deadline, the plane will fall out of the sky. Then there are realtime systems like VoIP where, if you don't meet the deadline, the call will cut out. And there is a desire to get "almost realtime" for things like VoIP on general purpose time sharing systems, where you want to deprioritize less latency sensitive tasks in order to hit the deadline if you can, but nobody dies if you don't. The trouble with using "real" realtime in those systems is that the system may not have enough capacity in theory even when it does in practice. In other words, if you have three concurrent realtime processes that could each in theory use up to 50% of the available resources at a time, but in practice almost never use more than 10% each, then for less critical systems you may be willing to bank on "almost never" not happening often enough to matter.
  - qznc 11y ago
    Imho "soft" and "hard" real time distinguish pretty well between "must meet deadline" and "should meet deadline". The only problem I see is that they sound so similar, although the development process is radically different between the two.
11thEarlOfMar 11y ago
I always enjoyed the rejoinder: "Real-fast is not real-time." 50 years ago, real-time in it's true sense was not a product or service attribute that humanity was much concerned with. Information was disseminated largely via 'latent' methods and the delay between and event and it's report was typically measured in hours at best, and months for people subscribing to magazines. Today, it does matter to an increasing number of people when an event occurred, and their desire to know 'soon' is increasing, because the reach of events has expanded to global extents and and the time we have to react is shrinking. Case in point: I've set a reminder to keep an eye on the Hang Seng in Hong Kong this evening to get an early read on where the NASDAQ will head tomorrow morning. These trends are pushing the term real-time/realtime/real time out of computer jargon and into mainstream where they must be oversimplified and therefore conflated, like so many others. It's the natural evolution of language.
tormeh 11y ago
Never take "realtime" seriously, unless it's prefaced with either "soft" or "hard".
- jacquesm 11y ago
  That's the whole point here. Soft realtime is not realtime, only hard realtime is realtime. So no need for prefixes.
  - luckydude 11y ago
    I don't know why you were downvoted, you are correct. Have an upvote.
  - dllthomas 11y ago
    I agree that (in a technical context) only hard-realtime is realtime, but a higher percentage of the things that say "hard realtime" mean realtime than of those that just say "realtime".
  - tormeh 11y ago
    Both terms have varying definitions, depending on who you ask. Realtime, to me, means that there are deadlines and that those deadlines can realistically be broken. Soft realtime means that given some conditions, the deadlines will be met, at least x% of the time. Hard realtime means that the deadlines will be met, unless there's a grave hardware malfunction. Then there's the hardness of deadlines, which is proportional to the consequence of missing them. A hard deadline means that a computational result is worthless if it's late.
uxcn 11y ago
Outside of engineering, it's just the reality that terms get co-opted a lot to mean things like fast or asynchronous. It's really engineering where the strict definitions are important, which is the only scenario I generally do try to correct.
bitwize 11y ago
"Realtime" in business means "on short enough timescales to significantly shorten your OODA loop" and could imply delays ranging from seconds to hours. Of course this is to be expected now that business has cozied up to technology to run at-sign the speed of thought: look at the sound flogging that suits have given to engineering terms like "interface", "bandwidth" and "offline".
Animats 11y ago
Having used QNX for a robot vehicle, I'm very aware of what "real time" means. If the computers didn't send an update to steering and throttle every 100ms, at 125ms a hardware stall timer cut the throttle and slammed on the brakes. A typical test of a real time OS such as QNX is to hook up a square wave generator to an interrupt input, and run a program which is activated by the interrupt. The program then turns on an output. The input and output signals are sent to an oscilloscope, so you can see the delay. In a true real time OS, there are no outliers where the delay is much longer than usual, even if there are other processes running.[1] [1] http://www.qnx.com/developers/docs/6.5.0/index.jsp?topic=%2Fcom.qnx.doc.ide.userguide%2Ftopic%2Fsysprof_Interrupt_latency_.html http://www.qnx.com/developers/docs/6.5.0/index.jsp?topic=%2F...
- luckydude 11y ago
  Who owns QNX these days? I was friends with Dan Hildebrandt who was one of the core OS guys, one of the few who could actually touch the microkernel. We had a lot of good OS conversations/discussions/arguments back in the day. It was a sad day in 1998 when we lost him.
  - Animats 11y ago
    Blackberry owns QNX now. QNX has gone from closed source to open source to closed source to open source to closed source. Along the way, most of its developer community bailed. Sad.
everyone 11y ago
Seems to be the fate of any cool-sounding term. Eg. 'Quantum' http://smbc-comics.com/index.php?db=comics&id=1841#comic http://smbc-comics.com/index.php?db=comics&id=1841#comic Though I must say the software industry is particularly guilty of stealing and corrupting terms from other fields. One particularly irksome example for me (as a former architect) is the word 'design'. When a software engineer says design he means css essentially, making it visually pretty. Whereas in architecture / engineering / industrial design etc. 'Design' means.. everything, the overall design or plan of your entire system. Thats just one small example that gets my goat up, there are tonnes more! ps. The votey (red button which you click for another little panel) is particularly good for that smbc! pps. Also as a game developer I reckon I'm safe using the term realtime if somethings being calculated at 60fps :) ie. realtime shadows vs. baked ones. If for example the shadows were lagging one frame behind everything else that would be unacceptable for a game.
- uxcn 11y ago
  Maybe marketing is another form of cargo cult.
- CountSessine 11y ago
  Though I must say the software industry is particularly guilty of stealing and corrupting terms from other fields. One particularly irksome example for me (as a former architect) is the word 'design'. When a software engineer says design he means css essentially, making it visually pretty. Whereas in architecture / engineering / industrial design etc. 'Design' means.. everything, the overall design or plan of your entire system. Thats just one small example that gets my goat up, there are tonnes more! I might agree with some of your other examples, but not this one so much. Software engineers, i.e. computer programmers who actually write design documents before they write code, have never used the word design for visually pretty. The word design has a separate and equally legitimate history coming from graphic design and world of commercial art and drafting. There's a not-insignificant intersection between that world and the world of front-end web programming where the word design is used to describe the a site's visual appeal and not the overall plan of the system.
  - 11y ago
bbcbasic 11y ago
I am confused by this. So is the problem that realtime 'should' just be used when there is a critical 'life threatening' problem if the deadline is not met, but to use realtime for a system that is not critical is seen as wrong? Lets say you have an algo controlling a fighter jet. That is realtime. If you had exactly the same algo in a 3d fighter pilot game. That should not be called realtime? Is this just an ego thing?
- jacquesm 11y ago
  No, it's a guarantees thing. If you can't guarantee your latency and scheduling then you're not real-time. So if you're doing something that you run on a jet that needs to be updated 5000 times per second +- 10us otherwise something breaks or the plane becomes uncontrollable then that's real-time. If it's a game version of the same you don't care about those guarantees because nothing would actually cause the plane to crash. Of course controlling the plane itself may not have such tight loops but plenty of processes active in the flying plane may very well have extremely tight constraints (for instance: engine management, especially near maximum power output). In real life there would be a penalty for missing an interrupt or a scheduled deadline, in a simulation everything would just happily hum along with a tiny delay. If you were simulating the real plane then you'd want your simulation to halt at that point so that you could figure out exactly what went wrong. One piece of hardware in our offices in Amsterdam long ago had a 'lost data' led latched so it would stay on if a fault condition ever happened no matter how briefly, if that led ever came on it meant going back to the drawing board because it indicated we were not in control of the machine to the extent that we thought we were.
  - eric-hu 11y ago
    > If it's a game version of the same you don't care about those guarantees because nothing would actually cause the plane to crash. > If you were simulating the real plane then you'd want your simulation to halt at that point so that you could figure out exactly what went wrong. Doesn't this all depend on the point of the simulation? For instance, the simulation could be an integration test of flight control systems. In which case, yes, you'd want the simulation to halt for debugging, as you stated. On the other hand, if the simulation is a networked flight sim trainer for pilots, then you would benefit from having the simulation do exactly what a plane would do in the real world. I think there's some insight in the OP's article, but I think he goes a bit too far. To me, "real time" has a domain specific meaning: there's a greater importance placed on time for this thing over that. That's a legitimate use of the word _in that domain_. If the world we we're living in were actually the Matrix, our use of "real time" wouldn't be less legitimate just because a plane crash is now bits changing instead of an actual plane crash.
jacquesm 11y ago
It's all about the guarantees. No guarantees: don't bother calling it real-time.

49 points by matt_d 11y ago

I think I have a pretty straight-forward answer to his question about its popularity: real-time became synonymous with instant results and zero delays to mainstream audiences. Not sure exactly from what sources but that's the common denominator across all of these usages.

bbrazil 11y ago
I think it's devolved beyond that into a marketing term, I've seen realtime mean anything from milliseconds to hours. I'd mostly interpret it as "faster than what you already have/are used to".
- TeMPOraL 11y ago
  I'd argue that GP is right, but only partially. It may be true that "real-time became synonymous with instant results and zero delays to mainstream audiences". But the story continues: then the sales&marketing folks and various other bullshitters noticed that "realtime = fast" and "fast = good", and they did what they always do - stared to stretch the term so that they can steal some of the good feelings associated with it, even though their products don't deserve them. It's what happened with the word "hacker", or is happening with the word "geek" right now. If something is associated with good qualities among relevant enough audience, it will be co-opted by marketing and then used and abused until it loses any meaning. That's what I hate about sales&marketing - it will fuck up everything that's cool. And journalism, I guess is to blame too (they are marketers too, competing for our attention). My pet peeve: ever heard about a company "going nuclear" or taking "a nuclear option"? That phrase should not be used to mean anything less serious than threatening to deploy an actual ICBM.
  - nickpsecurity 11y ago
    Your addition to my theory is probably right. I left it off just because I can't trace the specifics. Marketing and media are where I'd point the finger, though.
- detaro 11y ago
  I'd say that real-time covering hours is less a marketing artifact but part of the academic definition that real-time means that guaranteed timing limits are kept, whatever size they have.
- derefr 11y ago
  From the business analytics example, I think a useful layman's definition of "realtime" might be able to be extracted: "fast enough that, given the speed of the task the client is trying to accomplish, the client is never blocked waiting on the computation in such a way that it then performs suboptinally against its deadlines." In machine-assisted translation, "realtime" is whatever speed (milliseconds) is fast enough to have a conversation without pausing. In business, "realtime" is whatever speed (minutes/hours) is fast enough that the feed of information outpaces your ability to absorb and change strategy in response to the information. Interestingly, VR technology is "realtime" by both definitions: any perceptible latency (layman's definition) is unacceptable and causes feelings of "VR sickness"—so hard limits on frame delivery (technical definition) must be set. Or, "VR must be hard realtime in order to be realtime."
  - nickpsecurity 11y ago
    "I think a useful layman's definition of "realtime" might be able to be extracted: "fast enough that, given the speed of the task the client is trying to accomplish, the client is never blocked waiting on the computation in such a way that it then performs suboptinally against its deadlines."" That's actually a reasonable definition that could lead to re-interpretation and new usage by lay people. VR is a good example. Matter of fact, we did use that in game design because we had to differentiate between what had no delay and the pre-rendered graphics used in cut-scenes. We normally just said gameplay footage but some said "rendered in real-time." Those using VRML (the "VWWW") on dial-up knew what the opposite of real-time was. ;)
- rocky1138 11y ago
  I remember it really annoying me when I was in high school and I would see a minivan drive past that had "real time AWD." I think it was a Mazda, but I can't be sure. As though without it there would be some sort of batch processing delay when driving the car...?
  - nickpsecurity 11y ago
    Even the Flintstones didn't have to batch it all the way. Wonder who Mazda's real competition is?
VLM 11y ago
Real time used to be extremely difficult, therefore it was extremely well designed and engineered. Think of the engineering and quality level of a stereotypical multi-million dollar industrial machine with hard real time nanosecond level response. Jitter in the response rate can be measured and correlated with tool lifetime and product scrap rates, for example. Think like a PR guy, use some empathy: Isn't complicated well engineered high quality stuff cool and easy to sell? I know, we'll call our Angry Birds tablet "real time". After all if "real time" is a phrase that sells five axis milling machine motor control systems, think how well it'll sell thermostats? Sure the engineers will be pissed off at the bastardization of their technical term but I'm paid on commission so who cares what they think... if they complain I'll call them "hackers" again to shut them up, that usually works pretty well. Look how in mass media, "quantum" usually passes for the opposite of the technical physics definition. There is an inherent danger where theres a profit motive in divide and conqueor style separation of people, the makers vs the consumers could eventually become as bad as the UK vs US two cultures separated by a common language.

richmarr 11y ago

This title is literally true for me. During the 70s my dad & his team built a programming language & runtime environment for realtime control systems in power stations. It was called Cutlass, and it's still in (dwindling) use today. In my dad's context, the term 'realtime' drew the most useful distinction between types of system in that context. In the web days, the term is used slightly differently, but still draws broadly the most useful distinction within the context. And lastly in media, the tech industry and computer subcultures have a pretty bad track record of protecting words from mis-use... troll, hacker, repo, pull-request, etc. all have comically uninformed usage. You don't quarrel with folk who buy ink by the barrel, nor do you get far telling them that they're doing language wrong. Personally this isn't an issue I choose to care about, language is contextual after all, but even if you do my advice would be to save your blood pressure for a fight you have a hope of winning.

dwc 11y ago

Devolution/devaluation seems very common now. I'm not sure if it's my perspective or if it's really worse that it used to be. Some examples: * ROM: something you download and install on your Android phone (as opposed to socketing a new chip) * Machine Learning: any change in program behavior based on feedback input (we used to call this programming) * Disruptive: doing business at least slightly different than someone else (as opposed to a new paradigm that sends shockwaves through a whole industry) * Fork: make a copy of a project (as opposed to starting a rival project based on the codebase of another project)

oldmanjay 11y ago
Considering any of that "worse" is definitely your perspective. It's simple back-in-my-day-ism to apply a value judgment to language use.
- anon4 11y ago
  I used to be with "it". Then they redefined what "it" was and it wasn't what I was with. Now I can't be with what I used to be, because it's "it", but "it" is now different. In other words, embrace, extend, extinguish.
- UmDieWelt 11y ago
  The point is that the words don't really have a useful meaning anymore. It is especially important in technical topics to have terms with some specific meaning.
  - Retra 11y ago
    It's important to be able to construct specific meanings. You don't need terms to do that, and you run a major communication risk by relying on terms that you aren't willing to define. And if you define them first, then you can use them however you like.
    - kuschku 11y ago

luckydude 11y ago

I blame all the misguided folks who try and add "soft real time" to time sharing systems like Unix/Linux/etc. Anyone who does that has a profound misunderstanding of what real time is, it most definitely is not a time sharing system. If you want a time sharing system and real time, that problem has been solved, in a really elegant way. Victor Yodaiken did it years ago, he made a small real time kernel and he ran all of Linux as the idle process in the real time kernel. When Linux thought it was disabling interrupts it wasn't, only the real time kernel could do that. He had a demo where he was running xperf (or some fairly compute intensive X thing) while running tar cf - / | rsh someotherhost 'cat > /dev/null' while the real time kernel was gathering events. He never missed a deadline or dropped an event. Sweetest design I've ever seen, have your cake and eat it too.

AnthonyMouse 11y ago
> I blame all the misguided folks who try and add "soft real time" to time sharing systems like Unix/Linux/etc. Anyone who does that has a profound misunderstanding of what real time is, it most definitely is not a time sharing system. Part of the problem is that there are realtime systems where, if you don't meet the deadline, the plane will fall out of the sky. Then there are realtime systems like VoIP where, if you don't meet the deadline, the call will cut out. And there is a desire to get "almost realtime" for things like VoIP on general purpose time sharing systems, where you want to deprioritize less latency sensitive tasks in order to hit the deadline if you can, but nobody dies if you don't. The trouble with using "real" realtime in those systems is that the system may not have enough capacity in theory even when it does in practice. In other words, if you have three concurrent realtime processes that could each in theory use up to 50% of the available resources at a time, but in practice almost never use more than 10% each, then for less critical systems you may be willing to bank on "almost never" not happening often enough to matter.
- qznc 11y ago
  Imho "soft" and "hard" real time distinguish pretty well between "must meet deadline" and "should meet deadline". The only problem I see is that they sound so similar, although the development process is radically different between the two.

11thEarlOfMar 11y ago

I always enjoyed the rejoinder: "Real-fast is not real-time." 50 years ago, real-time in it's true sense was not a product or service attribute that humanity was much concerned with. Information was disseminated largely via 'latent' methods and the delay between and event and it's report was typically measured in hours at best, and months for people subscribing to magazines. Today, it does matter to an increasing number of people when an event occurred, and their desire to know 'soon' is increasing, because the reach of events has expanded to global extents and and the time we have to react is shrinking. Case in point: I've set a reminder to keep an eye on the Hang Seng in Hong Kong this evening to get an early read on where the NASDAQ will head tomorrow morning. These trends are pushing the term real-time/realtime/real time out of computer jargon and into mainstream where they must be oversimplified and therefore conflated, like so many others. It's the natural evolution of language.

tormeh 11y ago

Never take "realtime" seriously, unless it's prefaced with either "soft" or "hard".

jacquesm 11y ago
That's the whole point here. Soft realtime is not realtime, only hard realtime is realtime. So no need for prefixes.
- luckydude 11y ago
  I don't know why you were downvoted, you are correct. Have an upvote.
- dllthomas 11y ago
  I agree that (in a technical context) only hard-realtime is realtime, but a higher percentage of the things that say "hard realtime" mean realtime than of those that just say "realtime".
- tormeh 11y ago
  Both terms have varying definitions, depending on who you ask. Realtime, to me, means that there are deadlines and that those deadlines can realistically be broken. Soft realtime means that given some conditions, the deadlines will be met, at least x% of the time. Hard realtime means that the deadlines will be met, unless there's a grave hardware malfunction. Then there's the hardness of deadlines, which is proportional to the consequence of missing them. A hard deadline means that a computational result is worthless if it's late.

uxcn 11y ago

Outside of engineering, it's just the reality that terms get co-opted a lot to mean things like fast or asynchronous. It's really engineering where the strict definitions are important, which is the only scenario I generally do try to correct.

bitwize 11y ago

"Realtime" in business means "on short enough timescales to significantly shorten your OODA loop" and could imply delays ranging from seconds to hours. Of course this is to be expected now that business has cozied up to technology to run at-sign the speed of thought: look at the sound flogging that suits have given to engineering terms like "interface", "bandwidth" and "offline".

Animats 11y ago

Having used QNX for a robot vehicle, I'm very aware of what "real time" means. If the computers didn't send an update to steering and throttle every 100ms, at 125ms a hardware stall timer cut the throttle and slammed on the brakes. A typical test of a real time OS such as QNX is to hook up a square wave generator to an interrupt input, and run a program which is activated by the interrupt. The program then turns on an output. The input and output signals are sent to an oscilloscope, so you can see the delay. In a true real time OS, there are no outliers where the delay is much longer than usual, even if there are other processes running.[1] [1] http://www.qnx.com/developers/docs/6.5.0/index.jsp?topic=%2Fcom.qnx.doc.ide.userguide%2Ftopic%2Fsysprof_Interrupt_latency_.html http://www.qnx.com/developers/docs/6.5.0/index.jsp?topic=%2F...

luckydude 11y ago
Who owns QNX these days? I was friends with Dan Hildebrandt who was one of the core OS guys, one of the few who could actually touch the microkernel. We had a lot of good OS conversations/discussions/arguments back in the day. It was a sad day in 1998 when we lost him.
- Animats 11y ago
  Blackberry owns QNX now. QNX has gone from closed source to open source to closed source to open source to closed source. Along the way, most of its developer community bailed. Sad.

everyone 11y ago

Seems to be the fate of any cool-sounding term. Eg. 'Quantum' http://smbc-comics.com/index.php?db=comics&id=1841#comic http://smbc-comics.com/index.php?db=comics&id=1841#comic Though I must say the software industry is particularly guilty of stealing and corrupting terms from other fields. One particularly irksome example for me (as a former architect) is the word 'design'. When a software engineer says design he means css essentially, making it visually pretty. Whereas in architecture / engineering / industrial design etc. 'Design' means.. everything, the overall design or plan of your entire system. Thats just one small example that gets my goat up, there are tonnes more! ps. The votey (red button which you click for another little panel) is particularly good for that smbc! pps. Also as a game developer I reckon I'm safe using the term realtime if somethings being calculated at 60fps :) ie. realtime shadows vs. baked ones. If for example the shadows were lagging one frame behind everything else that would be unacceptable for a game.

uxcn 11y ago
Maybe marketing is another form of cargo cult.
CountSessine 11y ago
Though I must say the software industry is particularly guilty of stealing and corrupting terms from other fields. One particularly irksome example for me (as a former architect) is the word 'design'. When a software engineer says design he means css essentially, making it visually pretty. Whereas in architecture / engineering / industrial design etc. 'Design' means.. everything, the overall design or plan of your entire system. Thats just one small example that gets my goat up, there are tonnes more! I might agree with some of your other examples, but not this one so much. Software engineers, i.e. computer programmers who actually write design documents before they write code, have never used the word design for visually pretty. The word design has a separate and equally legitimate history coming from graphic design and world of commercial art and drafting. There's a not-insignificant intersection between that world and the world of front-end web programming where the word design is used to describe the a site's visual appeal and not the overall plan of the system.
- 11y ago

bbcbasic 11y ago

I am confused by this. So is the problem that realtime 'should' just be used when there is a critical 'life threatening' problem if the deadline is not met, but to use realtime for a system that is not critical is seen as wrong? Lets say you have an algo controlling a fighter jet. That is realtime. If you had exactly the same algo in a 3d fighter pilot game. That should not be called realtime? Is this just an ego thing?

jacquesm 11y ago
No, it's a guarantees thing. If you can't guarantee your latency and scheduling then you're not real-time. So if you're doing something that you run on a jet that needs to be updated 5000 times per second +- 10us otherwise something breaks or the plane becomes uncontrollable then that's real-time. If it's a game version of the same you don't care about those guarantees because nothing would actually cause the plane to crash. Of course controlling the plane itself may not have such tight loops but plenty of processes active in the flying plane may very well have extremely tight constraints (for instance: engine management, especially near maximum power output). In real life there would be a penalty for missing an interrupt or a scheduled deadline, in a simulation everything would just happily hum along with a tiny delay. If you were simulating the real plane then you'd want your simulation to halt at that point so that you could figure out exactly what went wrong. One piece of hardware in our offices in Amsterdam long ago had a 'lost data' led latched so it would stay on if a fault condition ever happened no matter how briefly, if that led ever came on it meant going back to the drawing board because it indicated we were not in control of the machine to the extent that we thought we were.
- eric-hu 11y ago
  > If it's a game version of the same you don't care about those guarantees because nothing would actually cause the plane to crash. > If you were simulating the real plane then you'd want your simulation to halt at that point so that you could figure out exactly what went wrong. Doesn't this all depend on the point of the simulation? For instance, the simulation could be an integration test of flight control systems. In which case, yes, you'd want the simulation to halt for debugging, as you stated. On the other hand, if the simulation is a networked flight sim trainer for pilots, then you would benefit from having the simulation do exactly what a plane would do in the real world. I think there's some insight in the OP's article, but I think he goes a bit too far. To me, "real time" has a domain specific meaning: there's a greater importance placed on time for this thing over that. That's a legitimate use of the word _in that domain_. If the world we we're living in were actually the Matrix, our use of "real time" wouldn't be less legitimate just because a plane crash is now bits changing instead of an actual plane crash.

jacquesm 11y ago

It's all about the guarantees. No guarantees: don't bother calling it real-time.