[rules-dev] else

[Geoffrey De Smet]

I like Mario's proposal because I can actually read it.
Those special chars | < are gibberish to me.

The only reason we're not debating to use a new readable, intuitive 
keyword, is because of the back-wards compatibility issues involved.
But using unreadable, unintuitive special char just for that, is 
probably not a good idea.
I wonder if we reserve new keywords by prefix them with reserved special 
char like "@"?
Then we can introduce as many keywords as we want without breaking 
backwards compatibility.

Who's our target users for DRL authors?
A) Supersmart computer science guys
B) Blue collar Java programmers
C) Domain experts (= not programmers)

I 'd classify "{notA} < A()" as (given some time to learn it) readable 
for A, but not for B and C.

Op 18-08-11 23:35, Mario Fusco schreef:
> Hi Mark,
>
> Since you're gathering 2 cents here and there I decided to add also 
> mine even if I am pretty sure that I am still missing the whole 
> picture and anyway at the moment I cannot see all the consequences of 
> what I am going to propose.
>
> To tell you the truth I find the label syntax not very intuitive and I 
> was wondering if we could avoid it in some way. In the end what the 
> 90% of the users are asking for is just something like:
>
> rule R
>     when
>         A()
>     then
>         do something
>     else
>         do something else
> end
>
> while we are going to give them something that is not exactly the same:
>
> rule R
>     when
>         {notA} < A()
>     then
>         do something
>     then.notA
>         do something else
> end
>
> In particular I was thinking if we could keep the when ... then ... 
> else syntax that should be familiar to the biggest part of the users 
> and at the same time obtain a flexibility similar to the one provided 
> by the labels syntax. Probably we could do it with a kind of nested 
> rules so, for instance, the rule:
>
> rule R1
>     when
>         {af} < A() > {at}
>         B()
>     then
>         DO
> then.af <http://then.af>
>         DO.af
> then.at <http://then.at>
>         DO.at
> end
>
> could be rewritten as it follows:
>
> rule R1
>     when
>         B()
>     then
>         DO
>         rule R1A
>             when
>                 A()
>             then
>                 DO.at
>             else
>                 DO.af
>         end
> end
>
> Of course the nested rule couldn't be used by the Drools engine as it 
> is, but we could implement a kind of "linearization" process at 
> compile time that translates it more or less as:
>
> rule R1_1
>     when
>         A()
>         B()
>     then
>         DO
>         DO.at
> end
>
> rule R1_2
>     when
>         not A()
>         B()
>     then
>         DO
>         DO.af
> end
>
> In the same way the "or" example:
>
> rule R1
> when
>     (     A() > {a1} or
>         B() > {b1} or
>         C() > {c1} )
>     D()
> then
>     DO
> then.a1
>     DO.a1
> then.b1
>     DO.b1
> then.c1
>     DO.c1
> end
>
> could be written as:
>
> rule R1
>     when
>         D()
>     then
>         DO
>         rule R1A
>             when
>                 A()
>             then
>                 DO.a1
>         end
>         rule R1B
>             when
>                 B()
>             then
>                 DO.b1
>         end
>         rule R1C
>             when
>                 C()
>             then
>                 DO.c1
>         end
> end
>
> and then linearized at compile time in a similar way as I wrote before.
>
> Once again I still haven't evaluated all the implications of my 
> suggestion neither I know if we can cover with it all the cases 
> proposed by Mark. I am pretty sure I am missing something important to 
> be honest, but since we are in a "brainstorming phase" I thought it 
> could worth to consider it at least.
>
> My 2 cents,
> Mario
>
>
> _______________________________________________
> rules-dev mailing list
> rules-dev at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-dev

-- 
With kind regards,
Geoffrey De Smet

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