On 18/08/2011 16:48, Geoffrey De Smet wrote:
My 2 cents

- I don't like using {} for something that doesn't contain code (the closer we stick to java the easier it is for our users to learn it).
It would be nice if would do some sort of annotations and then do:
  @ElseLabel else1 : A()
That way we can avoid adding new keywords or special chars (the latter which isn't intuitive in this case).

- It took me a couple of q&a with edson to understand how many time it would fire under which conditions.
I wonder if we really need this complexity if we can avoid DRY for the users in a more generic way.
For example, with ruleParts:

rulePart part1
when
   $p : Person( name == "darth" )
end

rulePart part2
when
   Address( person == $p, city == "deathstar" )
end

rule darthOnDeathstar
when
  $part1
  $part2
then
  sout("darth is home")
end

rule darthNotOnDeathstar
when
  $part1
  not ($part2)
then
  sout("darth is away")
end

This is lower level, but think about:
In the RHS, you can easily extract methods into java classes or DRL functions,
but on the LHS, this isn't possible, right?

This one would probably be address by looking properly into a Lisp like Macro system.

Mark

Op 18-08-11 16:48, Mark Proctor schreef:
The other consideration of "<" is that we are thinking of using |" for filters.
A() | distinct
It may be we can just achieve this with "|" so we only introduce a single symbol and the | can work to both the left or right side of a CE
{failabel1} | A() | {passlabel2}

which could also allow
A() | distinct | {passlabel2}

Mark
On 18/08/2011 15:03, Edson Tirelli wrote:

   Mark,

   The [] syntax for the labels will clash with the sequencing syntax we've been discussing. Possibly {} or a unique separator:

{else1} A()

else1 := A()

else1 ?= A()

   Considering that Patterns can also take bindings, probably {} is more distinct:

{else1} a : A()

   My vote:

when
    {else1} Person( name == "darth" ) // works on patterns
    A()
    {else2} B()
then
   ....
otherwise.else1
...
otherwise.else2
...
end

   Will we support unlabeled "else" as well?

when
    A() and B()
then
   ...
otherwise
   ...
end

   If so, what will be the semantics of it? What happens if an A() is inserted but not B()? vice-versa? What happens if C() is inserted?

   Regarding inline "consequences", at the moment I am not really a fan of it. I think it complicates the syntax unnecessarily at this point but I can be convinced. The support to else by itself is a big step forward as you know users frequently ask for that.

   My .02c.

   Edson
   

2011/8/18 Mark Proctor <mproctor@codehaus.org>
We have been looking into designs around else, so here are our initial
brain storming ideas, which aims at doing more than just else, but
handling signal processing like situations. "else" is always triggerd by
the failure of a left propagation. In effect an named "else" block is
just another terminal node that will result in an activation on the
agenda. It will have access to declarations prior to the failure of
propagation in the network.

// Possible syntaxes
[name] ( CE+ ) // no symbol
[name] | ( CE+ )
[name] < ( CE+ )

1)
when
    [name1] < Person( name == "darth" ) // works on patterns
    A()
then
   ....
then.name1
...
end

2)
when
    $p : Person( )
    [name1] < eval( $p.name == "darth" ) // works on evals
    A()
then
   ....
then.name1
...
end

3)
when
    [name1] < ( Person( name == "darth" ) and Address( city == "death
star" ) // works on groups
    A()
then
   ....
then.name1
...
end

This could actuall be extended to have inline "then" too. In this case
when their is a success propagation on that node it will result in an
activation placed on the agenda that has access to all the prior bound
declarations.

1)
when
    Person( name == "darth" ) > [name1]  // works on patterns
    A()
then
   ....
then.name1
...
end

2)
when
    $p : Person( )
    eval( $p.name == "darth" ) > [name1] // works on evals
    A()
then
   ....
then.name1
...
end

3)
when
   ( Person( name == "darth" ) and Address( city == "death star" ) >
[name1]  // works on groups
    A()
then
   ....
then.name1
...
end

This can be used with 'or'
when
    ( A() > [a1] or
      B() > [b1] or
      C() > [c1] )
   D()
then
...
then.a1
....
then.b1
....
then.c1
...
end

It's a little tricker but in theory we can do this before/afer the 'or' too
This can be used with 'or'
when
    [x1] < ( A() > [a1] or
                 B() > [b1] or
                 C() > [c1] )
                 D()
then
...
then.a1
....
then.b1
....
then.c1
...
then.x1
....
end

We could allow [name] as just an inline creation to an activation that
always passes, which with 'or' could provide a "default".
when
    [x1] < ( A() > [a1] or
                 B() > [b1] or
                 C() > [c1] or
                  [default] )
                 D()
then

Of course both could be supported at the same time
[afailed] < A() > [asuccess]


We could further allow just an inline code block, isntead of an inline
reference to a block {...code here...} instead of [name1].

We can also use this to do switch like operations, for erlang style
signal processing, although i'd like to see an improvemet to the syntax
here, just not sure what it would be...
$o : Object() from stream
( A() > [a] from $o or
  B() > [b] from $o or
  C() > [c] from $o )

Where as 'or' currently works like java's "|" single operator, i.e. all
logical branches are tested. We could add a short cut or operationr
'sor' that would work like "||", so once the first CE matches in an 'or'
block the rest are igored. We could even consider an 'xor' ....

Finally there is no reason why we couldn't allow other CE's after the <.
Which would provide for very rich signal processing. For instance. If
A() fails, it'll propagate to B, if B() fails it'll activate [a1]
[a1] < B() < A()
This can be nested and using using parenthesis to show groupings.
( [a1] < B() > [b2] ) < A()

Anyway more food for thought, enjoy :)

Mark



_______________________________________________
rules-dev mailing list
rules-dev@lists.jboss.org
https://lists.jboss.org/mailman/listinfo/rules-dev



--
  Edson Tirelli
  JBoss Drools Core Development
  JBoss by Red Hat @ www.jboss.com


_______________________________________________
rules-dev mailing list
rules-dev@lists.jboss.org
https://lists.jboss.org/mailman/listinfo/rules-dev

_______________________________________________ rules-dev mailing list rules-dev@lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-dev

-- 
With kind regards,
Geoffrey De Smet


_______________________________________________
rules-dev mailing list
rules-dev@lists.jboss.org
https://lists.jboss.org/mailman/listinfo/rules-dev