[rules-dev] Drools syntax diagrams - redrawn

[Mark Proctor]

  On 22/09/2010 14:40, Wolfgang Laun wrote:
> Service:
> http://www-cgi.uni-regensburg.de/~brf09510/syntax.html 
> <http://www-cgi.uni-regensburg.de/%7Ebrf09510/syntax.html>
>
> The grammar syntax is the same as used in DRL.g but stripped of all 
> the antsy additions, and simplified.
>
> @Mark: I'm well aware of the limitations of a 1:1 translation of a 
> parser's grammar into diagrams. I have reduced the splits into 
> separate rules in DRL.g considerably. But what do you want to hide 
> from the users? The syntax is the syntax, and there's no sweet-talking 
> around it after you have reduced all the noise from technical splits.
>
> One thing that might help would be deprecating things like infix or/and.
yes agreed. Simplifying the grammar, reducing ambigiiouty or multiple 
ways of doing the same thing, will make any resulting grammar both 
easier ot maintain and grok.

Edson, Davide and I have already discuss this. Both are working on a new 
parser and are trying to address these issues. So things that are doing are:

Single binding on 'or'
$binding : ( Pattern() || Pattern() )

We are thinking of only allowing 'or' between patterns and not allowing 
users to mix and match 'or' and '||'.  Inside of patterns '||' is the 
only connective allowed and will remain so.

We will also probably make a choice and only allow infix 'or' and 'and', 
at the moment users can chose infix or prefix. Personally I find prefix 
quite attractive as it works sort of like a "choice":
(or Person(  ... )
       Person( ... )
       Person( ...) )

But I think most peopel are more comfortable with infix:
(Person(  ... ) or
   Person( ... ) or
   Person( ...) )

return value, eval, literal constraint, variable constraint are going. 
These are left overs of a Clips based grammar. So instead we'll have a 
generic "expr" class that follow more common modern ASTs for expression 
engines, like say MVEL.

Davide has also requested that we make $ prefix mandatory for LHS 
bindings as that is deterministic and again makes the grammar cleaner. I 
personally like it being optional and it's still open to debate. But I 
recognise the need to have better maintained grammar, that is more 
consistent and regular with easy to main documentation.

Mark
>
> Some rules can be omitted if they coincide with Java's own rules; just 
> add an explanation.
>
> -W
>
>
> On 22 September 2010 14:56, Anstis, Michael (M.) <manstis1 at ford.com 
> <mailto:manstis1 at ford.com>> wrote:
>
>     What was the service and was it the ANTLR grammar you uploaded to
>     generate the images?
>
>     Thanks,
>
>     Mike
>
>     -----Original Message-----
>     From: rules-dev-bounces at lists.jboss.org
>     <mailto:rules-dev-bounces at lists.jboss.org>
>     [mailto:rules-dev-bounces at lists.jboss.org
>     <mailto:rules-dev-bounces at lists.jboss.org>] On Behalf Of Wolfgang Laun
>     Sent: 22 September 2010 13:38
>     To: Rules Dev List
>     Subject: [rules-dev] Drools syntax diagrams - redrawn
>
>     I've found this online service and stuffed the Drools grammar into it.
>
>     You may see the results while they are still there:
>     http://www-cgi.uni-regensburg.de/~brf09510/syntax.tmp/x45371x0x0x.ebnf.h
>     tml
>     <http://www-cgi.uni-regensburg.de/%7Ebrf09510/syntax.tmp/x45371x0x0x.ebnf.h%0Atml>
>     <http://www-cgi.uni-regensburg.de/%7Ebrf09510/syntax.tmp/x45371x0x0x.ebn
>     f.html
>     <http://www-cgi.uni-regensburg.de/%7Ebrf09510/syntax.tmp/x45371x0x0x.ebn%0Af.html>>
>
>     -W
>
>
>
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