[rules-users] missing parameters in the fact object

[Jai Vasanth]

Hi,

  I am using agenda groups to  pick sets of rules to fire based on an
attribute value. The presence or absence of other attributes  is dependent
on the value of this attribute based on which I select  a particular agenda
group.

Here is an example

rule "ABC"
  when
    Shape( type = "rectangle" )
  then
    drools.setFocus("twodimensional")
end


rule "PQR"
  when
    Shape( type = "cube" )
  then
    drools.setFocus("threedimensional")
end

rule "area threshold"
agenda-group "twodimensional"
  when
    Shape( area > 20 )
  then
    System.out.println ("large object" );
end

rule "volume threshold"
agenda-group "threedimensional"
  when
    Shape( volume > 20 )
  then
    System.out.println ("large object" );
end


Suppose if my shape object is a rectangle, then it wouldnt have the volume
attribute. In this case when we try to run these rules it would throw a
NoSuchElementException.

Is there a way to avoid this? Agenda groups help us fire the RHSs
conditionally, Is there a way by which I can conditionally fire LHS of
certain sets of rules ?


Thanks


Jai

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