Re: How to handle processes that must occur

Quoting Drew McDermott <drew.mcdermott@yale.edu>:

> > [Craig Schlenoff]
> > 
> > I have a process in my OWL-S representation that must occur. However,
> > it has a condition associated with it. Somehow I want to tell the
> > system to wait until the condition is true so that the process will
> > occur. The process is in a sequence list, and I am afraid that an
> > implementation of the OWL-S specification will skip to the next
> > step in the sequence if the condition is not met at that point in
> > the execution, which is not what I want to occur.

Would it skip?  I'd have thought, perhaps naively, that in a sequence,
if a precondition of a step was not satisfied, then execution could not
advance beyond that point.  The execution engine would do something
such as wait, or signal an error, or ask someone what to do.

> > One way to do this is to create a composite process that contains a
> > repeat-until ControlConstruct which states that the systems should
> > perform a "wait" activity until the condition is met and then it can
> > perform the desired process.

There'd also be the problem that the condition might be true
temporarily, so that the loop exits, and then go back to being false.
For instance, if you're waiting for a light to come on, the bulb
might blow as soon as it comes on, so that it's off again.

-- Jeff

Received on Monday, 19 April 2004 18:01:08 UTC