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?/*
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 <mproc...@codehaus.org
<mailto:mproc...@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 <http://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 <http://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
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Edson Tirelli
JBoss Drools Core Development
JBoss by Red Hat @ www.jboss.com <http://www.jboss.com>
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With kind regards,
Geoffrey De Smet
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