SADL conditional next event BNF for conditions
                       Jim Blythe, May 02

The old version:

>(a Event with
>   (next-event-test ('<expr>))
>   (next-event ((:args t (<event-expr>*))
>                (:args nil (<event-expr>*)))))

The current version:

(a Event with
   (next-event (<next-event-expr>*)))

<next-event-expr> = (if <expr> then (<event>+))     ;; 1 or more
                    | <event>*

Operational semantics: to find the next events for an event in a KM
situation, check ALL the conditions, and take the union of the events on
the right hand sides of those constructs whose conditions are true,
along with all non-conditional next events.

<expr>  = (<expr> [and <expr>]*)
	| (<expr> [or <expr>]*)
  	| (not <expr>)
  	| <test>


<test> =  (<path> = <val-or-path>)
	| (<path> /= <val-or-path>)
	| (<path> > <val-or-path>)
	| (<path> < <val-or-path>)
	| (<path> includes <val-or-path>)

<path> = (the <slot> of <instance-reference>)

<val-or-path> = <path>
              | <val>

<instance-reference> = <instance>
                     | <path>

<val> = <atomic-value> 
      | <property-value>

<atomic-value> = <symbol> | <string> | <number>

<property-value> = <scalar-value>
                 | <cardinal-value>

<scalar-value> = (:pair <symbol> <class>)

<cardinal-value> = (:pair <number> <UoM>)


Here, <instance> is an object that we can click on in the cmap. This can
include Self as Vinay noted before.