Re: [rules-dev] Backwards chaining: the difference between input and output variables

@ge0ffrey, *you* know "looc" is a typo, but "loc" could equally be an unused bound variable and "looc" an unused output value.

I find it difficult to see there is sufficient "context" to give a suitable error message - other than perhaps warning of unused bindings. @wolfgang, Your proposition works for slotted parameters; whereas the ";" allowed for positional parameters too. AFAIK the BC changes bring two discrete features: BC and positional parameters. @all I've expressed my "simpleton" view on how, as a user, I would best understand its operation. It isn't based upon science or a wealth of experience with a multitude of other programming languages; just a "feeling" of what I consider right. Being just a "feeling" I am happy to watch this discussion evolve and learn from others' experience. With kind regards, Mike On 21 April 2011 07:50, Geoffrey De Smet <ge0ffrey.spam(a)gmail.com <mailto:ge0ffrey.spam@gmail.com>> wrote: > and instead have the tooling inject what ever is necessary as a > visulation. > > Most questions we have to the user mailing list involve people > writing DRL not using tooling. IntelliJ users and NetBeans users don't have any (up-to-date) DRL tooling. Some Eclipse users I know don't install extra plugins such as the drools plugin out of fear of Eclipse instability. The new Eclipse plugin wont do that visualization yet either? I like Laun's and Manstis and mine proposal, as long as there's something in the syntax that makes it clear whether that food is - an input variable => constrains the rule, potentially decreasing the number of activations - an output variable => frees the rule, potentially increasing the number of activations And a typo shouldn't change the behavior from one to the other, it should give a compilation error. |rule| |typo2 ||when| |||Here( loc : location) | |||?||editableThings||(food, ||looc||;)||// looc is a typo of loc| |then| System.out.println("Food " + f + " at location " + loc); // Output: // Food crackers at location kitchen // Food apple at location kitchen // Food chocolate at location kitchen // BUG: that food is in the living room! // Food chips at location kitchen // BUG: that food is in the living room! |end | Op 21-04-11 08:27, Wolfgang Laun schreef: > Designing syntax well is not easy. With extensions, one should > strive for as much > conformity with the existing language, while trying to follow > general principles. > > One might have discussed (for instance) the use of field names > for referencing > the query relations, taken from their parameter definition. And > then one could write, > as usual: > > ?editableThings(food: thing, location == loc ) > > or > > ?editableThings(food: thing, loc: location ) > > And the in/out is clear to all who know a little legacy DRL. > > And the ugly semicolon evaporates. > > And the maintainability/readability disadvantage of "positional" > is gone. > > Cheers > -W > > > On 20 April 2011 22:52, Michael Anstis <michael.anstis(a)gmail.com > <mailto:michael.anstis@gmail.com>> wrote: > > > > Simple yes, but consistent too should be a factor. > > > > Most questions we have to the user mailing list involve people > writing DRL not using tooling. > > > > So DRL, IMO, has to be seen as the "tool" to author rules. Drop > the proposed colon altogether or make it's use consistent. > > > > On 20 April 2011 17:42, Mark Proctor <mproctor(a)codehaus.org > <mailto:mproctor@codehaus.org>> wrote: > >> > >> My personally opinion is to keep the language simple and > instead have the tooling inject what ever is necessary as a > visulation. Be it different colouring, hover over or graphic > symbol. It keeps the language simple and actually achieve the > desired result better. > >> > >> Mark > >> On 20/04/2011 14:00, Leonardo Gomes wrote: > >> > >> +1 for Michael's suggestion. > >> > >> It's a bit more verbose, but makes things clear. > >> > >> The semicolon here: > >> ?editableThings(food : ?, loc;) > >> > >> Is a typo, right? You actually meant: > >> > >> ?editableThings(food : ?, loc); > >> > >> - Leo. > >> > >> > >> > >> On Wed, Apr 20, 2011 at 11:59 AM, Michael Anstis > <michael.anstis(a)gmail.com <mailto:michael.anstis@gmail.com>> wrote: > >>> > >>> Hmmmmm.... > >>> > >>> Personally, I don't like the use of ":" i isolation as it's > what we currently use to bind variables and I feel "cheese:" as > an output definition could just make people question whether > they've missed something. Perhaps "cheese : ?" would be a viable > alternative. This would be in keeping with (a) current variable > declaration, (b) the use of "?" to identify a call to a query. > Geoffrey's examples would then become:- > >>> > >>> rule outputinput > >>> when > >>> Here( loc : location) > >>> ?editableThings(food : ?, loc;) > >>> then > >>> System.out.println("Food " + food + " at location " + loc); > >>> // Output: > >>> // Food crackers at location kitchen > >>> // Food apple at location kitchen > >>> end > >>> > >>> rule outputOutput > >>> when > >>> ?editableThings(food : ?, loc : ?;) > >>> then > >>> System.out.println("Food " + food + " at location " + loc); > >>> // Output: > >>> // Food crackers at location kitchen > >>> // Food apple at location kitchen > >>> // Food chocolate at location living room > >>> // Food chips at location living room > >>> end > >>> > >>> rule typo > >>> when > >>> Here( looc : location) > >>> ?editableThings(food : ?, loc : ?;) > >>> then > >>> System.out.println("Food " + food + " at location " + loc); > >>> // Output: > >>> // Food crackers at location kitchen > >>> // Food apple at location kitchen > >>> // Food chocolate at location living room > >>> // Food chips at location living room > >>> // looc is just an unused bound variable > >>> end > >>> > >>> On 20 April 2011 10:16, Geoffrey De Smet > <ge0ffrey.spam(a)gmail.com <mailto:ge0ffrey.spam@gmail.com>> wrote: > >>>> > >>>> Mark and I were discussing backwards chaining > >>>> > http://blog.athico.com/2011/04/backward-chaining-emerges-in-drools.html > >>>> on IRC and we 'd like your opinion on a design issue. > >>>> > >>>> The example > >>>> ======== > >>>> > >>>> Let's say you have this data: > >>>> Location("crackers", "kitchen") > >>>> Location("apple", "kitchen") > >>>> Location("chocolate", "living room") > >>>> Location("chips", "living room") > >>>> > >>>> Let's say you have this code: > >>>> > >>>> query editableThings( String thing, String location ) > >>>> Location(thing, location) > >>>> end > >>>> And then these 3 rules: > >>>> > >>>> rule outputinput > >>>> when > >>>> Here( loc : location) > >>>> ?editableThings(food, loc;) > >>>> then > >>>> System.out.println("Food " + f + " at location " + loc); > >>>> // Output: > >>>> // Food crackers at location kitchen > >>>> // Food apple at location kitchen > >>>> end > >>>> > >>>> rule outputOutput > >>>> when > >>>> ?editableThings(food, loc;) > >>>> then > >>>> System.out.println("Food " + f + " at location " + loc); > >>>> // Output: > >>>> // Food crackers at location kitchen > >>>> // Food apple at location kitchen > >>>> // Food chocolate at location living room > >>>> // Food chips at location living room > >>>> end > >>>> > >>>> rule typo > >>>> when > >>>> Here( looc : location) > >>>> ?editableThings(food, loc;) > >>>> then > >>>> System.out.println("Food " + f + " at location " + loc); > >>>> // Output: > >>>> // Food crackers at location kitchen > >>>> // Food apple at location kitchen > >>>> // Food chocolate at location living room > >>>> // Food chips at location living room > >>>> end > >>>> > >>>> The discussion > >>>> ========= > >>>> > >>>> Both rules have the same statement: > >>>> ?editableThings(food, loc;) > >>>> > >>>> In the outputInput rule, "loc" is an input variable. > >>>> In the outputOutput rule, "loc" is an output variable. > >>>> > >>>> I am wondering if we don't need a visual demarcation that a > variable is an output variable, > >>>> to make it stand out of an input variable? > >>>> > >>>> Proposition 1: Suffix output variables with ":" > >>>> > >>>> rule outputinput > >>>> when > >>>> Here( loc : location) > >>>> ?editableThings(food:, loc;) > >>>> then ... end > >>>> > >>>> rule outputOutput > >>>> when > >>>> ?editableThings(food:, loc:;) > >>>> then ... end > >>>> rule typo > >>>> when > >>>> Here( looc : location) > >>>> ?editableThings(food:, loc;) // compiler error because > input variable loc is not declared > >>>> then ... end > >>>> > >>>> -- > >>>> With kind regards, > >>>> Geoffrey De Smet > >>>> _______________________________________________ > >>>> rules-dev mailing list > >>>> rules-dev(a)lists.jboss.org <mailto:rules-dev@lists.jboss.org> > >>>> https://lists.jboss.org/mailman/listinfo/rules-dev > >>>> > >>> > >>> > >>> _______________________________________________ > >>> rules-dev mailing list > >>> rules-dev(a)lists.jboss.org <mailto:rules-dev@lists.jboss.org> > >>> https://lists.jboss.org/mailman/listinfo/rules-dev > >>> > >> > >> > >> _______________________________________________ > >> rules-dev mailing list > >> rules-dev(a)lists.jboss.org <mailto:rules-dev@lists.jboss.org> > >> https://lists.jboss.org/mailman/listinfo/rules-dev > >> > >> > >> _______________________________________________ > >> rules-dev mailing list > >> rules-dev(a)lists.jboss.org <mailto:rules-dev@lists.jboss.org> > >> https://lists.jboss.org/mailman/listinfo/rules-dev > >> > > > > > > _______________________________________________ > > rules-dev mailing list > > rules-dev(a)lists.jboss.org <mailto:rules-dev@lists.jboss.org> > > https://lists.jboss.org/mailman/listinfo/rules-dev > > > > > _______________________________________________ > rules-dev mailing list > rules-dev(a)lists.jboss.org <mailto:rules-dev@lists.jboss.org> > https://lists.jboss.org/mailman/listinfo/rules-dev -- With kind regards, Geoffrey De Smet _______________________________________________ rules-dev mailing list rules-dev(a)lists.jboss.org <mailto:rules-dev@lists.jboss.org> https://lists.jboss.org/mailman/listinfo/rules-dev _______________________________________________ rules-dev mailing list rules-dev(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-dev