Ability to negate a constraint group
------------------------------------
Key: JBRULES-1559
URL:
http://jira.jboss.com/jira/browse/JBRULES-1559
Project: JBoss Drools
Issue Type: Feature Request
Security Level: Public (Everyone can see)
Components: Drl Parser/Builder
Affects Versions: FUTURE
Reporter: Dirk Bergstrom
Assigned To: Mark Proctor
Priority: Minor
I want to write a rule that says "Find all long-eared dogs that do not have
short, black hair". This seems like the simple way to do it:
collect( Dog( ears=="long",
not (hair=="short" && color=="black")
)
But that doesn't parse. Some digging through the archives unearthed a mention
of De Morgan's laws, which leads to:
http://en.wikipedia.org/wiki/De_Morgan's_laws
Which explains that I can instead write:
collect( Dog( ears=="long", (hair!="short" ||
color!="black") )
Which, after some mental effort, turns out to be the right thing.
However, had I not found the reference to De Morgan's Law, it would have taken
me a long time to get there (if indeed I ever would have). The end result is
also quite difficult to parse if you're not a logician, and thus not very
user-friendly.
--
This message is automatically generated by JIRA.
-
If you think it was sent incorrectly contact one of the administrators:
http://jira.jboss.com/jira/secure/Administrators.jspa
-
For more information on JIRA, see:
http://www.atlassian.com/software/jira