Re: Can OO be successful in real-time embedded systems?

[Richard Riehle <rriehle@nunic.nu.edu>]

 Robert A Duff wrote:
 >
 > Run-time dispatching is just like a case-statement, except the branches
 > are scattered all over the code.  To do white-box testing, you have to
 > track down all overridings of a given procedure.  Having done that, it's
 > no harder than testing a case statement.  So, I think you want a tool to
 > do that tracking down.  I use "grep" for that purpose, but one could
 > imagine something more helpful.

   I am aware of the notion of dynamic case vis a vis dispatching. Also,
   the built-in safety of Ada 95 has not escaped my notice.

   However, in hard, real-time systems (HRTS), run-time dispatching is a
   little more of an issue than a simple case statement.  The controlling
   factor is whether we can predict that a certain sequence of actions
   will be time-determinate.

   Granted, there will be many situations where this will be easily
   predicted.  However, extensive use of run-time dispatching can, I
   believe, make it more difficult to predict the kind of timing
   requirements which often characterize HRTS software environents.

   Since Ada 95 is new, there is likely to be little experience with
   dispatching in HRTS.  I am simply suggesting that it be approached
   conservatively.  Perhaps I am just too much of a "scaredy-cat" about
   such things.  However, I know I am not alone in this concern.

   Richard Riehle