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

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

On 5 May 1996, Paul Carlton wrote:

> Absolutely!!!  And recommended!!!
>
> We have a full-blown real-time predictive dialer designed with
> Raumbaugh/CRC techniques and implemented in c++.  Runs like a
> screaming demon!!

  Agree.  Used carefully, and selectively, object technology can be
  an excellent approach to embedded systems.  The question is whether
  all aspects of OO technology are appropriate.

  Also, OO technology has been used on countless Ada embedded,
  real-time, safety-critical projects for years.  In fact, this
  has been a niche market for Ada in which OO has achieved a fair
  amount of respectability.

  The new Ada 95 standard raises the ante, and makes OO technology even
  more attractive for embedded systems.  Already, OOP projects, using
  Ada 95, are in process in both the defense and non-defense domain.

  A key question for Ada developers has been the reliability associated
  with dynamic binding.  That issue comes in two flavors.  1) Is it
  possible to dynamically invoke a wrong or non-existent method, 2) Can we
  predict with certaintly that we will always meet hard deadlines.  The
  first issue is easily accomodated under the rules of the new Ada
  standard.  The second is more difficult.  Since a method is selected
  at run-time, it is impossible to guarantee the deterministic properties
  one requires for hard, real-time schedules.

  The consequence of the above issue is that many embedded systems
  developers approach dynamic polymorphism with great caution -- even
  avoid it altogether. Fortunately, for those of us in the Ada community,
  we can benefit from all the other capabilities of OOP, such as
  inheritance and encapsulation,  while choosing to not to use dynamic
  polymorphism when it could be dangerously non-deterministic.

  Richard Riehle