Linked by Thom Holwerda on Mon 16th Apr 2007 20:56 UTC, submitted by BlueVoodoo
Java "This article, the first in a five-part series on real-time Java, describes the key challenges to using the Java language to develop systems that meet real-time performance requirements. It presents a broad overview of what real-time application development means and how runtime systems must be engineered to meet the requirements of real-time applications. The authors introduce an implementation that addresses real-time Java challenges through a combination of standards-based technologies."
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Laurence
Member since:
2007-03-26

"

Real-time != speed.
"

That really depends on the specification of the RT application (ie whether it's hard-RT or soft-RT)

To quote the article posted:

"Real-time (RT) is a broad term used to describe applications that have real-world timing requirements. For example, a sluggish user interface doesn't satisfy an average user's generic RT requirements. This type of application is often described as a soft RT application. The same requirement might be more explicitly phrased as "the application should not take more than 0.1 seconds to respond to a mouse click." If the requirement isn't met, it's a soft failure: the application can continue, and the user, though unhappy, can still use it. In contrast, applications that must strictly meet real-world timing requirements are typically called hard RT applications. An application controlling the rudder of an airplane, for example, must not be delayed for any reason because the result could be catastrophic. What it means to be an RT application depends in large part on how tolerant the application can be to faults in the form of missed timing requirements. "

Taking this into account, I think jasutton's point is more than valid.

Edited 2007-04-17 11:00

Reply Parent Score: 2

taos Member since:
2005-11-16

"must not be delayed" != "must not be slow"
What you quoted reinforces "Real-time != Speed".

RT is all about _predicable_ timing, not raw speed.

Reply Parent Score: 2

Laurence Member since:
2007-03-26

"

"must not be delayed" != "must not be slow"
What you quoted reinforces "Real-time != Speed".

RT is all about _predicable_ timing, not raw speed.
"

Firstly: How are slow response times and delays not the same thing?

Secondly: My quote reinforces that if slow response times affect the core criteria of the RT application then speed is /essential/.

Nobody was saying speed directly defines RT – just that if the criteria of application required less than 0.1 response then the application would have failed its specification. To use their example (again): Predictable timing is all good and well, but if you're developing an aeroplane rudder control (as per the example) then raw speed in the application is /essential/ regardless of what the umbrella term ‘RT’ covers.

So all of your pedantic arguing about the finites of computing definitions is just avoiding the point the original poster was trying to make: If response times in Java soft RT applications are slow, then where is the confidence that Java is the best solution (given the amount of options available to us these days) for applications which require near-instant hard RT response times?

[edited - messed up the quote]

Edited 2007-04-17 13:00

Reply Parent Score: 2

sbergman27 Member since:
2005-07-24

"""
What it means to be an RT application depends in large part on how tolerant the application can be to faults in the form of missed timing requirements.
"""

Perhaps some descriptions of different kinds of real time applications would help.

If the software operating the controls can miss an event and the result would be that the airplane would only *nearly* crash, or the reactor core would only *nearly* melt down, then that is soft real time.

But if the microprocessor in your convection oven fails to turn the oven off at exactly the right time, and as a result, you totally miss getting grand prize at the bake-off, then that is a hard real time application.

Opinions may differ, depending upon whether one is on the plane or at the bake-off.

Edited 2007-04-17 14:50

Reply Parent Score: 3