In the spirit of the production-rules-practical-pattern-cookbook, could
anyone elaborate on why a xorGroup is this powerful? Why and where would
it be used?
Thanks,
Peter
Ho, Alan wrote:
Doh !!! That was one of my favorite features :)
I found the concept of a "xorGroup" is a powerful replacement for the strategy
design pattern. In this case, every consequence is a concrete strategy. Based on the
condition, the rule engine selects one consequence (a.k.a a specific strategy) to use.
Regards,
Alan Ho
-----Original Message-----
From: Mark Proctor [mailto:[EMAIL PROTECTED]
Sent: Wednesday, April 12, 2006 11:32 AM
To: [email protected]
Subject: Re: [drools-user] How to express conditional logic via DRL - ?
There is no xor-group for 3.0. will be in 3.1
Mark
Ho, Alan wrote:
I vote no on having 'else'.
The switch statement is exactly the same as the "xorGroup" concept in DROOLS
(aka mutually exclusive rules). In DROOLs 3, how do you make a set of rules to be part of
an XOR group ?
Regards,
Alan Ho
-----Original Message-----
From: Dmitry Goldenberg [mailto:[EMAIL PROTECTED]
Sent: Tuesday, April 11, 2006 7:57 AM
To: [email protected]
Subject: RE: [drools-user] How to express conditional logic via DRL - ?
This is actually the reasong I went through- wanting to use Drools as a script execution
framework. Ideally, I'd like to see support for IF-THEN-ELSE and possibly SWITCH. As of
now, I don't see a need for any other "procedural" constructs but it seems to
me that IF-THEN-ELSE would be an immediate need for our users. It would be nice to have
explicit support for it, rather than a whole chapter in our doc explaining how to achieve
it with multiple rules in a rule-set.
Thanks,
- Dmitry
________________________________
From: Mark Proctor [mailto:[EMAIL PROTECTED]
Sent: Tue 4/11/2006 10:46 AM
To: [email protected]
Subject: Re: [drools-user] How to express conditional logic via DRL - ?
Unfortunately I'm finding that many people just cannot adjust to the
declarative and coupletely decoupled nature of a rule engine. The end result is
that Drools is used as a script execution framework.
Felipe Piccolini wrote:
Mark,
I could vote on this, I would vote no to the 'else'. The declarative
thing about rule engines is that: no procedural code. So if you
wanna do an 'else' condition you should re-think your rule and chack
if its well writen. Of course this is just MHO.
:)
Tuesday, April 11, 2006, 6:09:22 AM, you wrote:
I thought about adding 'else' but I couldn't decide on the best way
to implement it, as there are several possabilities. Also 'else' is
not considered declarative, so its a kinda of code smell. I'll llook
into this again in 3.1
Mark
Geoffrey Wiseman wrote:
On 4/10/06, Dmitry Goldenberg <[EMAIL PROTECTED]> wrote:
What is the timeframe for 3.1? Else/else if are very important to
what we're trying to do.
I can see how I can to the following with the method described by
Geoffrey:
if (A) then B else if (C) then D endif
I also want to be able to do the following:
if (A) then B else D endif
I imagine that the rule would have to be written as a combo of
if (A) then B endif
if (!A) then D endif
so that the conditions are complimentary...
Indeed, yes, that's how you'd handle it.
If it does make it into 3.1, that's a good thing in terms of
supporting the way people think, talk, and work in other languages,
but fundamentally, the same capabilities are there now -- they just require more typing.
- Geoffrey
--
Geoffrey Wiseman
--------------------------
Felipe Piccolini
[EMAIL PROTECTED]
