[rules-dev] Rule Parameters/Aliases

Wed Aug 6 03:53:10 EDT 2008

Hi, nice idea,

Yoni, in your case the aliases could be implemented as immutable wrapper
objects, that implement the same interfaces and just delegate to the wrapped
object (alternatively they could extend the object, however the rules will
need to do instanceof checking to avoid recursion)

example:
rule aliasRule
    when
        $diagnosis : Diagnosis(alias == "anemia")
    then
        insert(new DiagnosisAnemia($diagnosis));
end

rule businessRule
    when
        DiagnosisAnemia(code == "5")
    then
        //do something
end

The wrapper object should be immutable, otherwise when doing updates you'll
have to update both, alias and the original object.

You could have 2 rule packages - one for setting up aliases and one for
business logic, so that it will be separated

I hope this helps.
Regards,
Michal

On Wed, Aug 6, 2008 at 8:10 AM, Michael Neale <michael.neale at gmail.com>wrote:

> One thing that people missed that may be interesting is the fact aliasing.
>
> So in the simplest case this is simply renaming a fact so instead of:
>
> FooBar() in a rule, you could write YourFabulousObject(). That is clear
> enough.
>
> What would be interesting is the following:
>
> FooBar(someField == "abc") aliased too SomethingElse()
>
> so the someField == "abc" constraint is always implicitly applied.
>
> I could see this being useful, especially when generic facts are
> used.. this could be
>
> Thoughts - any one wanna have a crack at implementing this?
>
> On Sat, Jul 19, 2008 at 3:31 AM, Mark Proctor <mproctor at codehaus.org>
> wrote:
> > Found this:
> >
> http://www.ilog.com/products/jrules/documentation/jrules67/rtsohelp/wbg_config7.html
> > "A ruleset parameter is the equivalent of a global variable"
> >
> > So a ruleset parameter is nothing more than a global, so just use our
> > globals as is and you get IN_OUT capabilities. I would strongly advise
> you
> > against representing your entire model this way and just using evals.
> >
> > Mark
> >
> >
> > Mark Proctor wrote:
> >
> > Yoni Mazar wrote:
> >
> > Hi all,
> > We are at the begining of a new clinical decision-support project. We
> plan
> > using drools (using Eclipse) in order to manage and execute our
> > business logic. As part of our research, we also evaluated JRules which
> has
> > a feature that
> > is very important to us and we could not find in Drools.
> >
> > I've reference the ilog manual on in/out parameters if anyone doesn't
> know
> > what they are:
> >
> http://www.ilog.com/products/jrules/documentation/jrules67/rsruleset/rs_rls_parameters.html#1026848
> >
> http://www.ilog.com/products/jrules/documentation/jrules67/rsruleset/rs_rls_tskcreatingrulesetparams.html
> >
> > I don't see the difference between a global and an IN_OUT parameter, and
> I
> > don't see the value of specifically saying which parameters are IN and
> which
> > are OUT. It doesn't seem that parameters are facts, they are not asserted
> > into the engine and propagated through the working memory - atleaast I
> don't
> > think they are, the manual doesn't say clearly enough, it just says they
> can
> > be referenced from any ruleset component, which seems to be akin to how
> we
> > do globals.
> >
> > Unless we missed it out, we will probably try and add this functionality
> > ourselves.
> >
> > In JRules, one can define a ruleset (corresponds to a package) with
> > parameters. Each parameter has a datatype (a class), a direction
> > (in/out/inout), and an alias. Then, within the rules, the user can refer
> to
> > the parameter alias. For
> > example, a user can define a ruleset with the following parameters:
> > *class=LabResult, direction=in, alias=hemoglobin *class=LabResult,
> > direction=in, alias=creatinin
> > Then, within a rule, one can write: when hemoglobin.value<10 and
> > creatinin.value>34 then...
> >
> > We can do the same with globals, but what that actually means is you have
> a
> > rule that doesn't use any working memory objects, and you put the
> > constraints into one big eval - no pattern matching, so you are turning
> the
> > rule engine into a scripting engine rather than a production rule system.
> >
> > If they are indeed facts that allow for pattern matching, then it seems
> that
> > they constraint by the variable name rather than by object type. I've
> never
> > liked this, again why not just use mvel directly as a scripting engine.
> But
> > I have thought of how this would be possible, somethign I call Named
> Facts -
> > where asserted facts can be given a unique string identifier and a
> pattern
> > can be told to not only constraint against that object type, but also
> > against that variable name. However this is something that users can
> emulate
> > themselves now, by just putting an "identifier" field on their facts and
> > constraining on it in the pattern. If someone comes up with a clean way
> for
> > supporting named facts and provides a patch we will consider including
> it,
> > but it's not one of our priorities at the moment.
> >
> >
> > Now, the application retrieves the patient data accordingly (hemoglobin
> and
> > creatinine data separetly - even though they are of the same type) and
> sets
> > the ruleset parameters:
> ruleset.parameters.add("hemoglobin",hemoglobinFact)
> > ruleset.parameters.add("creatinin",creatininFact)
> > It is important that the definition of the aliases will be done outside
> of
> > the rule (and not by defining in-rule variables)
> >
> > This approach simplifies the rules since some of the filtering is being
> > applied externally (not in the rule itself)
> >
> >
> > sounds like it simplifies it, by turning it into a scripting engine where
> > all facts are variables with identifiers.
> >
> > Does someone has an idea how to bridge this gap using Drools? Are there
> any
> > workarounds that can be used in order to avoid changes in
> > code?
> >
> >
> > Hopefully my main paragraph above shows you how to emulate this.
> >
> > And here we can use your help:
> > We are new to Drools (and still have to dive into the big ocean of code
> that
> > exists). The following features
> >
> > 1) defining parameters (in the package level...something like import)
> > 2) adding in/out modifiers (can be used in LHS, RHS, or both)
> > 3) allowing assignment of aliases to parameters 4) adding such
> functionality
> > to the rule editor (auto-complete ,type safety)
> >
> > Where should we start?
> > Do you have any ideas that can help start this process (e.g. relevant
> > classes, modules)?
> > We would appreciate any help regarding any of the items in the list
> above.
> > Any hints, suggestions, directions, referals and so on.
> >
> >
> > IF IN_OUT params are nothign more than globals and big fat evails, then
> you
> > have nothing to do.
> >
> > If they are named facts, it won't be easy, but you could try the
> following
> > approach:
> > 1) update drools to support named facts, as described previously, this
> will
> > involve a special type of ObjectType I imagine, and you'll have to change
> > how it matches ObjectTypes so that it also has access to the possible
> > variable name.
> > 2) figure out a sane syntax, that is not ambigious, to allow pattern
> > matching on named facts, and update our Antlr files to support this.
> > 4) I don't konw if in/out parameters are useful for a stateful session,
> or
> > only stateless. Either way you will probably want to create some Context
> > object that contains these parameters and then you "insert" them using
> > smething like insertWithParameters( myParams ). With stateless it'll
> execute
> > and return results directly, with stateful you'll have to figure out how
> > that'll work with possible incremental inserts and fireallrules being
> called
> > separately.
> > 4) Write lots of tests ot make sure it doesn't break anything
> >
> > Thanks a lot.
> >
> > Yoni
> >
> >
> >
> >
> >
> > _______________________________________________
> > rules-dev mailing list
> > rules-dev at lists.jboss.org
> > https://lists.jboss.org/mailman/listinfo/rules-dev
> >
> >
>
>
>
> --
> Michael D Neale
> home: www.michaelneale.net
> blog: michaelneale.blogspot.com
> _______________________________________________
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> rules-dev at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-dev
>
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