[rules-users] Find facts in partially matching LHS

[Wolfgang Laun]

I'd tackle this with a set of rules according to:

First, a rule that collects everything a customer has bought. Then,
low-priority rules matching defined Status sets with accumulated sets; this
checks whether  a customer has reached a certain status. Other rules detect
customer sets that are subsets of status sets and these can easily compute
the missing complement.

It may be of advantage to implement a set relation "subset of" as a custom
operator, which isn't difficult.

Status sets can be composed by some external tool and injected during
startup. This will keep all rules generic.

-W


2011/2/4 David Jacobsson <david.jacobsson at netlight.se>

>  Hi,
>
> I'm currently working with a system where we have customers with different
> status flags. This could look something like:
>
> customer has bought a car and a bicycle -> "wheel" status
> customer has bought a tent, a jacket and food -> "camper" status
>
> Since these rules can be quite complex and change often using Drools would
> be a good way so solve the problem. The problem now is that we want to
> answer the question, what's needed to achieve "camper" status? When it
> comes to DRL this becomes that we want to know which LHS facts that are
> missing for the "camper" rule to fire, i.e. so we can tell the customer that
> in order to achieve "camper" status you also need to buy a tent when he/she
> already have bought a jacket and food.
>
> The solution we have so far is to add a number of "negative" rules in DRL
> that can identify the missing facts. Our concern though is that this doesn't
> scale since these extra rules become several more then the base rules that
> define the statuses.
>
> Is it possible to solve this in a general way with Drools, i.e. to find
> missing facts leading to a specific conclusion?
>
> And example of status rule in DRL would look something like:
> -----
> when
>    BoughtCar( $c : customer )
>    BoughtBicycle( customer == $c )
> then
>    insert( new WheelStatus( $c ) );
> end
> -----
>
> The example above is of course just an example and not actual rules from
> our system.
>
> Regards,
> David
>
>
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