[jboss-jira] [JBoss JIRA] (DROOLS-664) Implement xpath notation in drools constraints

[Mario Fusco (JIRA)]

Mario Fusco created DROOLS-664:
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             Summary: Implement xpath notation in drools constraints
                 Key: DROOLS-664
                 URL: https://issues.jboss.org/browse/DROOLS-664
             Project: Drools
          Issue Type: Feature Request
            Reporter: Mario Fusco
            Assignee: Mario Fusco


It is required to allow an xpath notation in drools constraints like the following:

{code}
Person( $pet : /pets ) 
{code}

that is formally equivalent to the more verbose:

{code}
Person( $pets : pets )
$pet : Pet() from $pets
{code}

It should be also possible to have conditions filtering the collection like in:

{code}
Person( $pet : /pets[ age == 5 ] )
{code}

corresponding to:

{code}
Person( $pets : pets )
$pet : Pet(age == 5) from $pets
{code}

Of course also multiple indirections has to be allowed, so the following:

{code}
Man( $toy : /wife/children/toys )
{code}

will be equivalent to:

{code}
$man: Man( $wife: wife )
$child: Child() from $wife.children
$toy: Toy() from $child.toys
{code}

In this case the xpath notation will also allow to flatten the 2 from nodes in a single one that will internally flatten the collection of collections. Since it is necessary to distinguish the case when we want to iterate a collection from the case when we want to bind the collection as a whole it is possible to mix the collection iteration operator '/' and the simple dereferencing operator '.' as in:

{code}
Man( $toys : /wife/children.toys )
{code}

In this last case this pattern binds each List<Toy> for each child as a whole, so this is equivalent to:

{code}
$man: Man( $wife: wife )
Child( $toys: toys ) from $wife.children
{code}




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