September 2008 - rules-users - Jboss List Archives

Exception executing eval predicate in a Split node (RuleFlow)

by Sangrish

hey guys I am getting the exception : ----------------------------- Exception in thread "main" org.drools.RuntimeDroolsException: Exception executing predicate eval( mhc!=MIN_INT.intValue() ) at org.drools.rule.PredicateConstraint.isAllowed(PredicateConstraint.java:216) at org.drools.reteoo.AlphaNode.assertObject(AlphaNode.java:137) at org.drools.reteoo.CompositeObjectSinkAdapter.propagateAssertObject(CompositeObjectSinkAdapter.java:318) at org.drools.reteoo.ObjectTypeNode.assertObject(ObjectTypeNode.java:162) .................... ------------------------------- while executing the predicate : Author1( eval( mhc!=MIN_INT.intValue() ) ) in the condition part of a Split node in a ruleflow where, Author1 is a class defined as: ------------------------------ package com.sample; public class Author1 { public int mhc = -1; public Author1() {} public int getMhc() { return mhc; } public void setMhc(int y) { mhc = y; }; } ---------------------------- and MIN_INT is a global Integer (duly set and imported as global through the Split node constraint editor) I have not been able to understand the reason for it. Please enlighten me. Secondly, I am not able to have the concerned condition without "eval" predicate which I heard is not good performance wise. I think that without "eval" the Right Hand Side of a condition cannot have a non-constant. More enlightenment!!! :) I am using Drools Eclipse Plugin : 4.0.7 Thanks Siddharth -- View this message in context: http://www.nabble.com/Exception-executing-eval-predicate-in-a-Split-node-... Sent from the drools - user mailing list archive at Nabble.com.

15 years, 7 months

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Exception executing eval predicate in a Split node (RuleFlow)

by Sangrish

hello I am getting the exception : ----------------------------- Exception in thread "main" org.drools.RuntimeDroolsException: Exception executing predicate eval( mhc!=MIN_INT.intValue() ) at org.drools.rule.PredicateConstraint.isAllowed(PredicateConstraint.java:216) at org.drools.reteoo.AlphaNode.assertObject(AlphaNode.java:137) at org.drools.reteoo.CompositeObjectSinkAdapter.propagateAssertObject(CompositeObjectSinkAdapter.java:318) at org.drools.reteoo.ObjectTypeNode.assertObject(ObjectTypeNode.java:162) .................... ------------------------------- while executing the predicate : Author1( eval( mhc!=MIN_INT.intValue() ) ) in the condition part of a Split node in a ruleflow where, Author1 is a class defined as: ------------------------------ package com.sample; public class Author1 { public int mhc = -1; public Author1() {} public int getMhc() { return mhc; } public void setMhc(int y) { mhc = y; }; } ---------------------------- and MIN_INT is a global Integer (duly set and imported as global through the Split node constraint editor) I have not been able to understand the reason for it. Please enlighten me. Secondly, I am not able to have the concerned condition without "eval" predicate which I heard is not good performance wise. I think that without "eval" the Right Hand Side of a condition cannot have a non-constant. More enlightenment!!! :) I am using Drools Eclipse Plugin : 4.0.7 Thanks Siddharth -- View this message in context: http://www.nabble.com/Exception-executing-eval-predicate-in-a-Split-node-... Sent from the drools - user mailing list archive at Nabble.com.

15 years, 7 months

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Storing RuleDescr and/or PackageDescr in a database table

by imraan

Users in my system will be able to configure their own rules to an extent through a UI. I will create these rules programmatically using the org.drools.lang.descr package. Right now, I am trying to see if its possible to store the RuleDescr or PackageDescr object(s) in a database. Is there another way to store these objects in a database besides storing the contents of a DRL dump? Thanks, Imraan -- View this message in context: http://www.nabble.com/Storing-RuleDescr-and-or-PackageDescr-in-a-database... Sent from the drools - user mailing list archive at Nabble.com.

15 years, 7 months

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first steps with drools.....first errors

by Nicola Benaglia

Hi, I am moving my first steps with Drools 4.0.7. In my case I have an exam result to valuate. I can pass an ExamDetailas fact containing (value, authLimit, lawLimit) where authLimit may or may not be present. How can I force to valuate a rule only if a property exists? Here an example: rule "Rule n.1" dialect "mvel" no-loop true salience 10 when exists ExamDetail(authLimit); $examDetail : ExamDetail( $value: value < authLimit); then System.out.println( "1 Exam passed!" + $value); end rule "Rule n.2" dialect "mvel" no-loop true salience 10 when not exists ExamDetail(authLimit); ExamDetail( $value: value < lawLimit); then System.out.println( "2 Exam passed! + $value); end With these 2 rules I expected to cover my 2 cases: 1) When I have authLimit --> rule #1 2) When authLimit is absent --> rule #2 But I get this error (when I don't have authlimit): Exception in thread "main" org.drools.rule.InvalidRulePackage: [14,21]: unknown:14:21 Unexpected token 'authLimit'[25,6]: unknown:25:6 Unexpected token 'exists'[25,24]: unknown:25:24 Unexpected token 'authLimit' at org.drools.rule.Package.checkValidity(Package.java:424) at org.drools.common.AbstractRuleBase.addPackage(AbstractRuleBase.java:394) at eu.tecnoprogetti.rules.seam.ExamCheck.main(ExamCheck.java:23) Any suggestions? Thank you for your time. Nico

15 years, 7 months

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Drools Research Network Launched

by Mark Proctor

http://blog.athico.com/2008/09/drools-research-network.html The number of research projects around Drools is growing, however I've noticed that institutes are generally not aware of each others efforts. For this reason I'm launching the Drools Research Network. This consists of a web page (synced from a wiki page so anyone can edit) that shows all the University stakeholders in Drools and the various research projects. Please do help keep this page up to date and comprehensive. There is also a mailing list that is strictly for institute staff to discuss existing and potential projects, fundings, students and general collaboration to increase and improve Drools related research - if you fit in this category please subscribe. Drools Research Network home page <http://www.jboss.org/drools/research-network.html> The Wiki Page <http://wiki.jboss.org/wiki/DroolsResearchNetwork> The Mailing List <https://www.redhat.com/mailman/listinfo/drools-research>

15 years, 7 months

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UseCase: Drools in Engineering

by Michael Zimmermann

HI Edson, while discussing custom operators in drools trunk, you pocked me repeatedly to write something about how we use drools in a research project in the field of engineering. Here you go... may be it is also helpful or at least interesting for the other readers on this list :-) The Scope: Naval Engineering, In naval engineering vessels consists of thousands of parts (read: way more than an aircraft has today). Focusing on the steel structure, most of these parts are 2-dimensional plates of a certain size, thickness, grade and contour. For most fields of applications detailed regulations from classification societies etc. exist. Currently, the design of such objects is done using specialized CAD systems. Here the following issues are present in all cad systems and the design process today: - design time is 6 - 18 months (and not 10 - 15 years as for an air plane) - this means concurrent design, i. e. different people are working on parts or features that are closely related (strength, fatigue, cost, functional aspects or just being in the same room) on different levels of granularity (changing the hull 6 weeks before building happens!) - and no connection between design intent (specification on paper), design conditions (regulations, by the customer, results of calculations) and design solution chosen. Result: - We just have the geometrical data, nothing more in the CAD-model - No automatic checks if a certain component is changed; no automatic tests if a chosen design solutions really satisfies the conditions at lowest cost today - Therefore, changes (which you can't avoid) are cost intensive and error prone. Also, no one really knows why a certain solutions was chosen Enter Logic & Drools The objective of our research is to make the design process context aware. Example: If I design a "door" in a watertight "wall" the cad system should check whether the selected door is a watertight model. So, using one of the most popular commercial cad systems for naval engineering the approach is to define the standards (currently paper-based) electronically using DROOLS. Also, context-information like watertight, stress level=x ... is added to the model and reused in the design process. For standard design tasks (in a part of the field of detailed steel structural design) we use drools to completely automate the design process, i. e. - find a design problem in the model - select a suitable solution adhering to all known boundary conditions - design the solution - and assign a assurance level for the solution (how good is it?) Lessons Learnt from an Engineering POV 1) Extracting the knowledge is hard 2) Formulating it logically sound even harder (even official regulations are vague on a regular basis) 3) Defining the context a solution is valid for is even more difficult. 4) Current CAD systems in naval engineering are not really capable to store meta information and to interface with other applications. Lessons Learnt from a Drools POV 1) Drools is quite a nice system :-) 2) With DSL even engineers can use it (once they are trained how to "Think Rules". And that is next to impossible) 3) What's missing is some solution to easily define classes, class hierarchies and (!) instance data. We use OWL for now. eCore might be usable yet is terrible from a UI usability perspective 4) Not drools is the problem but getting the data in and out! 4a) The Smooks binding could be a godsend for this 4b) Fact templates sound really promising if you think dynamically generated classes via web services... What's missing in Drools? - An OWL/RDF binding would be really great (we use OWL to define, edit, store our standards. But encountered the clash of open world logic (DL) and closed world logic (CS) more than once.) I know there is quite a large interest for such a solution in the Ontology user base. - Better support for constraint programming (what we do here and there) for simple primitive cases (read: selection processes) would help. Drools solver is overkill; drools rules can not handle this if you think optional constraints. The custom operator "== (open world style)" we talked about helps, though. Well, it has gotten longer than I expected yet only skimmed the surface of our approach, I think. Hopefully not to long :-) cu, Michael

15 years, 7 months

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Drools Research Network

by Mark Proctor

I'm trying to get together a single source of knowledge on all the drools related research going on and various institutes involved. I've setup a wiki page to capture this information, if you are able to add to it please do. It contains a list of the projects, as well as the universities and mentors associated with Drools research. http://wiki.jboss.org/wiki/DroolsInAcademia The wiki page can be edited by anyone who has registered and logged in, the registration link should be on the top of the page. Mark

15 years, 7 months

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Drools & "Query by Example"?

by Michael Zimmermann

Hi there, I am not really sure what is the best approach to model this the drools way... So, what is the best approach using drools to find all objects of a known type that fulfil certain criterias? Caveat: The number of criterias is flexible and not known? I know, that such a selection process can be defined as simple case of constraint programming. Afaik this could be a problem for any rulebased system. Yet we do not want to introduce another compontent as this leads to dependency and communication issues. Example: Assume a class book with properties "author", "year", "id" and "publisher". As our problem is more complex I want to test book instances for the properties "author", "year" etc. in individual rules. Now, given a list of books in the working memory I want to get answer to the following questions: - List all books with author="myName", id="123" - List all book with publisher="Frank" Due to the closed world assumption in Java and hence Drools, what is not possible is: rule "MyRule" when book(year==myYear, author==myAuthor ...) then .... This works only if all properties myYear, myAuthor ... are present. If one is undefined, the rule does not match. The System: The system uses drools quite successfully for many tasks. All data objects are persisted using db4o. Currently, I can think of two different approaches: 1) - Start with all objects in the working memory - For each condition, if present, flag all objects, that do not fulfil this condition, as invalid - Afterwards, list / process all objects that are not marked as invalid 2) - Start with no object in the working memory - Construct a blank object of the type analyzed - If a certain condition is present, add this conidtion to the object - Query the object database in db4o and add all valid matching object to the working memory. (db4o supports QueryByExample) The double negotiation in the first approach is hard to understand and difficult to maintain. The second approach works reasonably well yet moves some of the main application logic to another component. So, any clues, pointers or ideas how to solve this problem in a better way? cu, Michael

15 years, 7 months

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Adding a custom operator to drools?

by Michael Zimmermann

Hi there, you might see this as a follow up to a discussion named "Query by Example" a couple of days ago, see here: http://lists.jboss.org/pipermail/rules-users/2008-September/006520.html Question to the devs: Having looked through the code, adding support for a custom operator requires - changing the DRL.g - regenerating the DRLLexer and DRLParser classes from this grammar - changing the XyzEvaluator and related classes in org.drools.base.evaluators. If I skip MVEL, the BRMS and other places like decision tables for now, is this all to expand the DRL syntax? Or are any further steps required to connect the grammar with the "java logic"? Thanks! Michael

15 years, 7 months

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RE: [rules-dev] Implementation of expert system

by Kumar, Prasoon (Prasoon)

This is a question for users group. Prasoon Kumar Technical Architect | Event Processor, Avaya | Tower 11, 5 Floor , Cybercity, Pune 4110028 -India | Voice: +91 20 4101 8119 | email: kumar4(a)avaya.com | mobile: +91 9922963102 ________________________________ From: rules-dev-bounces(a)lists.jboss.org [mailto:rules-dev-bounces@lists.jboss.org] On Behalf Of Binyala, Krishna Gopal IN BLR SISL Sent: Wednesday, September 17, 2008 4:11 PM To: rules-dev(a)lists.jboss.org Subject: [rules-dev] Implementation of expert system Hello, I am new to drools community... I want to develop an expert system for medical application using drools. can you please let me know how to use history data in drools... Because as far as i know we have to keep all the data in the working memory to access. How should i implement such system? Would be better if you can provide some reference to existing expert system implemented using drools. Thanks in advance. Krishna Gopal In three words I can sum up everything I've learned about life: it goes on... Important notice:This e-mail and any attachment thereto contains corporate proprietary information. If you have received it by mistake, please notify us immediately by reply e-mail and delete this e-mail and its attachments from your system. Thank You.

15 years, 7 months

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rules-users September 2008