7:11 a.m.
In this scenario I do have typical Order and Items data structure. I want to
implement various business rules where I want to check both Order attributes
and Item attributes together.
Order [ Date, Discount, Amount, Customer, Type, Items]
Item [ Quantity, Rate, ExpiresDate, Grade ]
I am trying to implements following rules but all gives me syntax error. I
wondering if someone can help me in.
rule “one”
when
Order ( $discount : Discount, $items : Items)
Item ($discount > 10 && Grade > 3) from $items
then
System.err.print(“Discount is not allowed with items having grade 3 or
higher)
end
rule “two”
when
Order ( $discount : Discount, $items : Items)
Item ($discount > 20 || Quantity < 5 ) from $items
then
//do some thinge
end
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7:43 a.m.
Discount is a field of Order and must not appear in an Item(...).
Probably you want:
Order ( $discount : Discount > 10,...
Also, most likely, all your fields need to be written with a lower case
initial letter,
Order ( $discount : discount > 10, $items : items)
-W
On Tue, Feb 23, 2010 at 1:11 PM, dhari <sdhari(a)hotmail.com> wrote:
In this scenario I do have typical Order and Items data structure. I want
to
implement various business rules where I want to check both Order
attributes
and Item attributes together.
Order [ Date, Discount, Amount, Customer, Type, Items]
Item [ Quantity, Rate, ExpiresDate, Grade ]
I am trying to implements following rules but all gives me syntax error. I
wondering if someone can help me in.
rule “one”
when
Order ( $discount : Discount, $items : Items)
Item ($discount > 10 && Grade > 3) from $items
then
System.err.print(“Discount is not allowed with items having grade 3
or
higher)
end
rule “two”
when
Order ( $discount : Discount, $items : Items)
Item ($discount > 20 || Quantity < 5 ) from $items
then
//do some thinge
end
--
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http://n3.nabble.com/Using-Collections-in-LHS-tp386923p386923.html
Sent from the Drools - User mailing list archive at Nabble.com.
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5:27 p.m.
Hi W
I know about case sensitivity issue. How can I combine both Order and Item in
one condition. I tried all possibilities but getting syntax error.
For example:
Order ($items : items, $discount : discount > 10, Item(grade > 3)
from $items) // gives error
Can please code this condition correctly for me?
Dhari
Date: Tue, 23 Feb 2010 13:43:01 +0100
From: wolfgang.laun(a)gmail.com
To: rules-users(a)lists.jboss.org
Subject: Re: [rules-users] Using Collections in LHS
Discount is a field of Order and must not appear in an Item(...).
Probably you want:
Order ( $discount : Discount > 10,...
Also, most likely, all your fields need to be written with a lower case initial letter,
Order ( $discount : discount > 10, $items : items)
-W
On Tue, Feb 23, 2010 at 1:11 PM, dhari <sdhari(a)hotmail.com> wrote:
In this scenario I do have typical Order and Items data structure. I want to
implement various business rules where I want to check both Order attributes
and Item attributes together.
Order [ Date, Discount, Amount, Customer, Type, Items]
Item [ Quantity, Rate, ExpiresDate, Grade ]
I am trying to implements following rules but all gives me syntax error. I
wondering if someone can help me in.
rule “one”
when
Order ( $discount : Discount, $items : Items)
Item ($discount > 10 && Grade > 3) from $items
then
System.err.print(“Discount is not allowed with items having grade 3 or
higher)
end
rule “two”
when
Order ( $discount : Discount, $items : Items)
Item ($discount > 20 || Quantity < 5 ) from $items
then
//do some thinge
end
--
View this message in context:
http://n3.nabble.com/Using-Collections-in-LHS-tp386923p386923.html
Sent from the Drools - User mailing list archive at Nabble.com.
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6:12 p.m.
I think what you are looking for is the following. Someone please
correct me if I am incorrect.
when
Order($discount : discount > 10, $items: items)
Item(grade > 3) from $items
then
System.err.print("Discount is not allowed with items having grade 3 or
higher");
This would fire when an Order has a discount greater than 10 and an
item with a grade greater than 3.
Not sure why you even need the $discount variable. You could just do
Order(discount > 10, $items : items) for the first line of the when
clause.
From: rules-users-bounces(a)lists.jboss.org
[mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Shabbir Dhari
Sent: Tuesday, February 23, 2010 5:27 PM
To: rules-users(a)lists.jboss.org
Subject: Re: [rules-users] Using Collections in LHS
Hi W
I know about case sensitivity issue. How can I combine both Order and
Item in one condition. I tried all possibilities but getting syntax
error.
For example:
Order ($items : items, $discount : discount > 10, Item(grade > 3) from
$items) // gives error
Can please code this condition correctly for me?
Dhari
________________________________
Date: Tue, 23 Feb 2010 13:43:01 +0100
From: wolfgang.laun(a)gmail.com
To: rules-users(a)lists.jboss.org
Subject: Re: [rules-users] Using Collections in LHS
Discount is a field of Order and must not appear in an Item(...).
Probably you want:
Order ( $discount : Discount > 10,...
Also, most likely, all your fields need to be written with a lower case
initial letter,
Order ( $discount : discount > 10, $items : items)
-W
On Tue, Feb 23, 2010 at 1:11 PM, dhari <sdhari(a)hotmail.com> wrote:
In this scenario I do have typical Order and Items data structure. I
want to
implement various business rules where I want to check both Order
attributes
and Item attributes together.
Order [ Date, Discount, Amount, Customer, Type, Items]
Item [ Quantity, Rate, ExpiresDate, Grade ]
I am trying to implements following rules but all gives me syntax error.
I
wondering if someone can help me in.
rule one
when
Order ( $discount : Discount, $items : Items)
Item ($discount > 10 && Grade > 3) from $items
then
System.err.print(Discount is not allowed with items having grade
3 or
higher)
end
rule two
when
Order ( $discount : Discount, $items : Items)
Item ($discount > 20 || Quantity < 5 ) from $items
then
//do some thinge
end
--
View this message in context:
http://n3.nabble.com/Using-Collections-in-LHS-tp386923p386923.html
Sent from the Drools - User mailing list archive at Nabble.com.
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6:28 p.m.
Thanks Jeffery.
I'll try this but what if I have more complex condition e.g.
Order ($discount : discount, $items : items)
Item(grade > 3 && (quantity < 5 || $discount > 10)) from $items
Date: Tue, 23 Feb 2010 15:14:18 -0800
From: ml-node+412055-2130217977-80541(a)n3.nabble.com
To: sdhari(a)hotmail.com
Subject: Re: Using Collections in LHS
I think what you are looking for is the following. Someone
please correct me if I am incorrect.
when
Order($discount : discount
10, $items: items)
Item(grade > 3) from
$items
then
System.err.print(“Discount is not
allowed with items having grade 3 or higher”);
This would fire when an Order has a discount greater than 10 and
an item with a grade greater than 3.
Not sure why you even need the $discount variable. You
could just do Order(discount > 10, $items : items) for the first line of the
when clause.
From:
[hidden email]
[mailto:[hidden email]] On Behalf Of Shabbir Dhari
Sent: Tuesday, February 23, 2010 5:27 PM
To: [hidden email]
Subject: Re: [rules-users] Using Collections in LHS
Hi W
I know about case sensitivity issue. How can I combine both Order and Item in
one condition. I tried all possibilities but getting syntax error.
For example:
Order ($items : items, $discount : discount > 10,
Item(grade > 3) from $items) // gives error
Can please code this condition correctly for me?
Dhari
Date: Tue, 23 Feb 2010 13:43:01 +0100
From: [hidden email]
To: [hidden email]
Subject: Re: [rules-users] Using Collections in LHS
Discount is a field of Order and must not appear in an Item(...).
Probably you want:
Order ( $discount : Discount > 10,...
Also, most likely, all your fields need to be written with a lower case initial
letter,
Order ( $discount : discount > 10, $items : items)
-W
On
Tue, Feb 23, 2010 at 1:11 PM, dhari <[hidden email]>
wrote:
In this scenario I do have typical Order and Items data structure. I want to
implement various business rules where I want to check both Order attributes
and Item attributes together.
Order [ Date, Discount, Amount, Customer, Type, Items]
Item [ Quantity, Rate, ExpiresDate, Grade ]
I am trying to implements following rules but all gives me syntax error. I
wondering if someone can help me in.
rule one
when
Order ( $discount : Discount, $items : Items)
Item ($discount > 10 && Grade > 3)
from $items
then
System.err.print(Discount is not allowed with items
having grade 3 or
higher)
end
rule two
when
Order ( $discount : Discount, $items : Items)
Item ($discount > 20 || Quantity < 5 )
from $items
then
//do some thinge
end
--
View this message in context:
http://n3.nabble.com/Using-Collections-in-LHS-tp386923p386923.html
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2:37 a.m.
You really ought to read all the pertaining sections in the Drools Expert
manual and experiment. Nobody can write complex rules without some exercise.
2010/2/24 dhari <sdhari(a)hotmail.com>
Thanks Jeffery. I'll try this but what if I have more complex
condition
e.g.
Order ($discount : discount, $items : items)
Item(grade > 3 && (quantity < 5 || $discount > 10)) from $items
Again, you are using a condition on discount not next to the field in the
fact where it occurs (i.e., Order); it's just not possible to write it this
way.
Order( discount > 10, $items : items ) # all Orders where discount > 10
Item( grade > 3, quantity < 5 ) from $items # and each of its Items where
grade > 3 and quantity < 5
There is no need to use && to combine two conditions for the same fact.
Now if you need to detect Order Items with grade > 3 where either the
quantitiy of the Item is < 5, or the Order's discount > 10, (or both)
you'd
have to write
Order( $discount : discount, $items : items ) # all Orders
Item( grade > 3, $quantity : quantity) from $items # and each of its Items
where grade > 3
eval( $discount > 10 || $quantitiy < 5 ) # and discount > 10 or quantity < 5
(or both)
-W
12:32 p.m.
Am 24.02.2010 08:37, schrieb Wolfgang Laun:
You really ought to read all the pertaining sections in the Drools
Expert manual and experiment. Nobody can write complex rules without
some exercise.
2010/2/24 dhari <sdhari(a)hotmail.com <mailto:sdhari@hotmail.com>>
Thanks Jeffery. I'll try this but what if I have more complex
condition e.g.
Order ($discount : discount, $items : items)
Item(grade > 3 && (quantity < 5 || $discount > 10)) from $items
Again, you are using a condition on discount not next to the field in
the fact where it occurs (i.e., Order); it's just not possible to
write it this way.
Order( discount > 10, $items : items ) # all Orders where discount > 10
Item( grade > 3, quantity < 5 ) from $items # and each of its Items
where grade > 3 and quantity < 5
There is no need to use && to combine two conditions for the same fact.
Now if you need to detect Order Items with grade > 3 where either the
quantitiy of the Item is < 5, or the Order's discount > 10, (or both)
you'd have to write
Order( $discount : discount, $items : items ) # all Orders
Item( grade > 3, $quantity : quantity) from $items # and each of its
Items where grade > 3
eval( $discount > 10 || $quantitiy < 5 ) # and discount > 10 or
quantity < 5 (or both)
Hi!
Another technique we commonly use at my employer to break up overly
complex rules is to "factor out" subexpressions, preferrably using
locally declared fact types to express the subexpressions, e. g.:
declare ItemPreventingDiscount
item: Item
order: Order
reason: String
end
rule "Prevent discount > 10 for items graded > 3"
when
$order: Order(discount > 10, $items: items)
$item: Item(grade > 3) from $items
then
ItemPreventingDiscount fact = new ItemPreventingDiscount();
fact.setItem($item); // optional
fact.setOrder($order); // optional
fact.setReason("discount percentage > 10 not valid for items graded >
3");
insertLogical($fact);
end
// add more rules to prevent other combinations of discount, quantity,
... whatever
rule "Issue error message if items preventing discount exist"
when
exists( ItemPreventingDiscount( $reason: reason, $item: item ) )
then
System.out.println("Discount not allowed: Item '"+
$item.getDescription() + "' prevents discount because " + $reason +
".");
end
One might debate whether it is already appropriate to factor out
subexpressions for this still rather simple example, yet our experience
is that in general it leads to code with an improved readability. I'd go
so far to suggest that whenever you're struggling with the syntax of the
language you're using to solve a problem, ask yourself whether you're
trying to achieve too much with too little code. The answer is of course
depending on your level of experience with the language, nevertheless
you (the author of the code) probably want to be able to read and
understand the code at any time.
Kind regards
Ansgar
1:08 p.m.
2010/2/24 Ansgar Konermann <ansgar.konermann(a)googlemail.com>:
rule "Issue error message if items preventing discount exist"
when
exists( ItemPreventingDiscount( $reason: reason, $item: item ) )
The exists isn't correct here; it prevents binding for $reason and
$item used on the RHS.
then
System.out.println("Discount not allowed: Item '"+
$item.getDescription()
+ "' prevents discount because " + $reason + ".");
Probably should use a retract on the ItemPreventingDiscount here.
Creating these XPreventingY facts would really make sense if they are
later combined into a single error report against the Order.
-W
end
5180
days inactive
5181
days old
7 comments
5 participants
participants (5)
-
Ansgar Konermann -
dhari -
Jeffrey Schneller -
Shabbir Dhari
-
Wolfgang Laun