[rules-users] how do you select from a global List in decisiontable

[Wolfgang Laun]

A (single or joined) cell below CONDITION must contain something that
results in a valid pattern when

   1. a pair of parentheses is appended
   2. the constraint(s) resulting from the cells below are inserted into
   these parentheses

Looking at "person: Person,  op: Person from otherPersonList", you realize
that "person: Person, op: Person" is not a valid CE, not even if you omit
the comma  Also, the cell cannot end with "from otherPersonList".

A constraint (2 rows down from CONDITION) is expanded with values from cells
below it by appending "==" and the cell value.

Apart from the basic design flaw Greg has pointed out: you can add a from
clause by using an additional column with "from otherPersonList" in the 3rd
row after RuleTable and an 'x' in each of the value cells.

You will also have to change the constraint "person.getRelationShip(op) ==
..." into an eval since this isn't correct constraint syntax.

-------------------------------
   CONDITION
   person: Person() op: Person
   activity
   PLAYING
-----------------------------
   CONDITION

   from otherPersonList
   x
------------------------------
   CONDITION

   eval( "$param".equals( person.getRelationShip(op) ) )
   FRIEND
-------------------------------


I suggest that you try and write your rules in DRL first before you start
thinking about decision tables. As you can see, certain conditions and CE
combinations cannot be expressed in tables. After all, a row of cells is
linear, but the syntaxl of LHS expression includes non-linear (recursive)
structures.

-W



2011/1/13 Gregory Mace <gregorymace at earthlink.net>

> Here is a simple example where 'otherPersonList' is a global
> java.util.List:
>
> RuleTable Are friends having fun
> CONDITION CONDITION ACTION
> person: Person,  op: Person from otherPersonList
> person.getRelationShip(op) op.getActivity() System.out.println("$param");
> FRIEND PLAYING Your friend is having fun
> ENEMY WORKING Not your friend and not having fun
>
> which produces the following drl output:
>
> #From row number: 31
> rule "Friends are having fun_31"
>
>
> when
> person: Person, op : Person from otherPersonList(person.getRelationShip(op)
> == "FRIEND", op.getActivity() == "PLAYING")
> then
> System.out.println("Your friend is having fun ");
> end
>
> #From row number: 32
> rule "Friends are having fun_32"
>
>
> when
> person: Person, op : Person from otherPersonList(person.getRelationShip(op)
> == "ENEMY", op.getActivity() == "WORKING")
> then
> System.out.println("Not your friend and not having fun");
> end
>
> shouldn't the 'from' be after the statement like this:?
>
> person: Person, op : Person(person.getRelationShip(op) == "ENEMY",
> op.getActivity() == "WORKING") from otherPersonList
>
> Thx
>
> On Jan 13, 2011, at 11:47 AM, Wolfgang Laun wrote:
>
> I think I understand your question, but I'm not sure how to answer it. ;-)
>
> What, exactly, are you trying to do? "Pulling" from a list means what?
>
> -W
>
>
> On 13 January 2011 20:34, Gregory Mace <gregorymace at earthlink.net> wrote:
>
>> I believe I have the list set up correctly as a variable, but I am not
>> sure how to set up a condition that pulls from a global list.  Any examples?
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