3:50 p.m.
Funny you should bring that up, I was just having this debate with a co-worker. :)
A decision table is a means for defining rules, not working memory objects. So no, out of
the box a decision table as it's defined in drools (and other rule management systems)
would not serve that purpose. However, there's no reason why you couldn't parse a
spreadsheet (or other tabular data format) to generate Data objects.
Now, are you sure it's Data objects you want to generate? I'm guessing from how
your question was phrased that it's Query objects you'd like to generate. In that
case the answer to the question is still no, but...if you use Wolfgang's approach to
solve the problem (i.e. defining the queries in the rules themselves, and not in a working
memory object) then using a decision table is appropriate. In fact, it's probably the
best way to define the rules. (It's most compact and readable when you have many rules
with a repetitive structure.)
--- On Wed, 11/11/09, Wishing Carebear <wishing.carebear(a)gmail.com> wrote:
From: Wishing Carebear <wishing.carebear(a)gmail.com>
Subject: Re: [rules-users] some pointers for solution
To: "Rules Users List" <rules-users(a)lists.jboss.org>
Date: Wednesday, November 11, 2009, 3:38 PM
Hi Greg:
Is it possible to use decision table to populate the
Data object that contains the criteria list
information.
Thanks,
Ravi
2009/11/8 Greg Barton <greg_barton(a)yahoo.com>
There
are a couple of ways to do this. I'm sure there's
a bit more clean way than the example I'm providing, but
this should get you in the right direction. It's not
100% rules, because it involves a bit of java collections
trickery. (See attached project,
collection_DroolsCriteriaMatch.tar.gz)
The heart of it is a single rule:
rule "Match"
when
d : Data()
q : Query( size <= d.size )
Number( intValue == q.size )
from accumulate(
Criteria( this memberOf d, this memberOf q ),
init( int total = 0; ),
action( total ++; ),
reverse( total --; ),
result( total )
)
then
System.out.println("Match: " + d + "
and " + q) ;
end
The Data object holds data to be queried, Query objects are
asserted to match the Data, and Criteria objects can be
contained in either. (With the aforementioned collections
trickery that if a Criteria is contained in a Query it can
be found in a Data object, but the reverse isn't true.
See the Query.contains(Object) method for how that's
implemented.)
So the rule above basically says "There's a Data
object, and all of the Query objects Criteria are contained
in the Data object."
There's an alternate way of doing this using eval and a
bit more java fu. See the eval_DroolsCriteriaMatch.tar.gz
project attached. This one's probably not optimal,
though, as it's basically a brute force check of all
Data objects against the asserted Query.
I tried for a while to get a solution working with
different criteria types from both Data and Query objects
being asserted into working memory, but I couldn't get
the accumulate syntax right. Anyone know of a way to do
that? (I figure that would get a "pure rules"
solution.)
--- On Sat, 11/7/09, Wishing Carebear <wishing.carebear(a)gmail.com>
wrote:
> From: Wishing Carebear <wishing.carebear(a)gmail.com>
> Subject: [rules-users] some pointers for solution
> To: rules-users(a)lists.jboss.org
> Date: Saturday, November 7, 2009, 10:19 PM
> Hello:
> There are n selection criteria from s1 .. sn for each
> item i1.. in. Each item can have a subset of criteria
which
> applies to them.
>
> The end user, can choose a subset of criteria like c1
> and c5 and only the item that has c1 and c5 valid
should be
> returned. For example: if item i1 and i2 have
criterias
> valid for c1, c2, c5, c6, c8 since the request is only
for
> criteria c1 and c5, i1 and i2 must be returned.
>
>
> Is it possible to write a rule using drools for this
> requirement.
>
> Thanks for your help and time,
> cabear
>
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