rule breakpoints

[GoogleCodeExporter]

Support for rule breakpoints, to simplify debugging of update rules.

It should be possible to somehow mark a rule as a breakpoint, so that when
the system tries to apply it, it will communicate with the developer/user
what is going on: which rule it is testing, and whether or not its
preconditions are currently true.

When prompted, the user should be asked whether to break execution and/or
show the current information state, or continue execution.

Original issue reported on code.google.com by [email protected] on 16 Dec 2009 at 10:46