[rules-users] How to write rules with optional parts?

[Wolfgang Laun]

In this particular case you can do

 $p1:person (name=="Alice")
 $p3:person (name=="David", this after[0,1] $p1)
 not person (name != "Bob", this after[0,1] $p1 && before[0,1] $p3 )

A more general approach should be possible by monitoring states rather than
event sequences, especially if you process events in real time.

1) Alice => state := A
2a) David => OK
2b) Bob  => state := AB
2c) Edward => state := _

And so on.
-W



On 20 July 2011 22:21, Edward Johnson <ejohnson at coderyte.com> wrote:

> How do you do rules that are a sequence of events where some of them are
> optional?
>
> Example:
>
> Alert if DAVID enters a room after ALICE or after ALICE and BOB
> If it were a string, this is roughly equivalant to the regex /ALICE( BOB)?
> DAVID/
>
> So:
> Alice then David => alert
> Alice then Bob then David => alert
> Alice then Charles then David => no alert
>
> I could write this as two rules but as the rules get more complex it could
> by hard to manage the resulting combatorial explosion.  Here it is as two
> rules:
>
> Rule 1:
>  $p1:person (name=="Alice")
>  $p2:person (name=="David", this after[0,1] $p1)
>
> Rule 2:
>  $p1:person (name=="Alice")
>  $p2:person (name=="Bob", this after[0,1] $p1)
>  $p3:person (name=="David", this after[0,1] $p2)
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