Business Rules Exchange

The APOCRIF POC, developed by ILOG, explores the possibility of serializing/deserializing an IRL ruleset as an XML RIF document as a first step. It will help to send rules between two different rule engines, JRules and JBoss rules.

It has been developped with Java 5.0. The following assumptions have been been set:

• The only common data model used by the rule engines is a schema provided by Mismo organization
• The only data processed by the rule engine are represented as XML document provided by the Mismo organization, following the previous schema specification.
• The rule engine shares the same Java model (JDK5.0) such a way any native method invocation has a meaning on both engine platforms.

The current state of the RIF core draft http://www.w3.org/2005/rules/wg/core/draft-20070323.html, limited to Horn clauses, does not permit to represent general production rules defined against object models such Java. However, a first analysis of the MISMO IRL rules proposed by Bruno Trimouille shows that a limited extension of the RIF core meta-model may be enough to serialize them as a RIF document.

APOCRIF Global architecture

Sharing same RIF metamodels

We propose to center the rule translation process around the meta-model of RIF. This meta-model is represented by a set of classes defined in the apocrif.core Java package. Those factory classes help to represent a RIF ruleset as a Java object tree.

This meta-model module provides an important RIF-XML serialization/deserialization service. The apocrif.core Java module could be shared among different engine implementations, factorizing the meta-model structure and its RIF-XML serialization.

The apocrif.pr (Production Rules) package, built upon the apocrif.core module, is a factory of RIF production rules. The data model is based on XML schema types and the procedural model is the libraries of Java 5.0.

Rule engine drivers

On top of the apocrif.pr package, we introduce a driver layer in charge of adapting the RIF rules and their meta-model to a dedicated rule language (IRL, JBoss rule). The driver API is likely to define the following method:

serialize: engine ruleset –> RIF ruleset
deserialize: RIF ruleset –> engine ruleset

Rule mapping

This section shows how production rules and object model notion could be mapped into RIF. The mapping is not unique. We try to reduce the needed extension of the RIF meta-model.

This mapping is described as a table given just below. In order to illustrate this table by affective examples, a MISMO rule is listed below.

The MismoRoot type is the mapping type of an XML complex type defined in the XML schema mismo.xsd. We assume for the moment that every type appering in a rule expression is related to an XML type.

rule Occupancy_Adjustments_1
{
  when {
     ?r : MismoRoot ();
     evaluate( ?r.division.equals( "wholesale"); ?r.occupancy.equals("Investors")  );
  }
  then {
    ?r.occupancyAdjustment = 0.95d;
  }
}

PR concept	RIF concept	Comment
( All )== operatorbinary operator !=, gt…dynamic field getterdynamic field setterdynamic object typeequals methodfrom conditional generatorin conditional generatorjava constantmethod invocationnative field getternative field setternative java typeright statementrule propertiesruleset nameruleset propertiesuniversal variable declarationvariable declaration with initialisation	( All )atomicatomic equaldedicated uniterm equalsdedicated uniterm getterdedicated uniterm setterextending core meta modelnative xsd corresponding typenot supportednot supportedrelated unitermrelated xml type constantvaraible constraints fromgeneratoropvaraible constraints ingeneratoropvariablevariable + constraintxml related type	( All )?a: a() from myterm represented in the constraint part of the rule as uniterm ( fromgeneratorop, var(?a), myterm )?a: a() in myterm represented in the constraint part of the rule as uniterm ( ingeneratorop, var(?a), myterm )?r.division is represented as uniterm(“xmlgetter”, “mismoroot”, “division”, var(“?r”) )?r.occupancyadjustment is represented like uniterm(“xmlsetter”, “mismoroot”, “occupancyadjustment”, var(“?r”), const(0.95) )?z == 2 is represented as equal( var(“z”), const(2) )?z.equals( “wholesale”) is represented as equal( var(“z”), const(“wholesale”) )for example ?x < 50 represented as uniterm( “xpath:numeric-less-than”, var(?x), const(50) )for example, java.lang.string is mapped on xsd:string. obviously, it exists some java types that can’t be represented in xml.inserted in the variables slot of the productionruleint ?i = 2 translated into var ( “?i” ) and uniterm ( “aprif:variableconstraintop”, var(“?i”), const(2) ) as a rule constraint.is it necessary for mismo rules ?is the priority important for mismo rules?only one statement in the right part (horn clause)the mismoroot type will be mapped on its related xml type.we add an attribute in the ruleset class.“hello” represented as const ( xsd:string, “hello”)
Native Java type	Native XSD corresponding type	For example, java.lang.String is mapped on xsd:string. Obviously, it exists some Java types that can’t be represented in XML.
Dynamic Object type	XML related type	The MismoRoot type will be mapped on its related XML type.
Native Field getter	not supported
Dynamic Field getter	Dedicated uniterm getter	?r.division is represented as Uniterm(“xmlGetter”, “mismoRoot”, “division”, Var(“?r”) )
Native Field setter	not supported
Dynamic Field setter	Dedicated uniterm setter	?r.occupancyAdjustment is represented like Uniterm(“xmlSetter”, “mismoRoot”, “occupancyAdjustment”, Var(“?r”), Const(0.95) )
Equals method	Dedicated uniterm equals	?z.equals( “wholesale”) is represented as Equal( Var(“z”), Const(“wholesale”) )
== operator	Atomic Equal	?z == 2 is represented as Equal( Var(“z”), Const(2) )
Java constant	Related XML type constant	“Hello” represented as Const ( xsd:string, “Hello”)
Method invocation	not supported	Is it necessary for MISMO rules ?
universal variable declaration	Variable	inserted in the variables slot of the ProductionRule
Binary operator !=, gt…	related uniterm	for example ?x < 50 represented as Uniterm( “xpath:numeric-less-than”, Var(?x), Const(50) )
Variable declaration with initialisation	Variable + Constraint	int ?i = 2 translated into Var ( “?i” ) and Uniterm ( “aprif:variableConstraintOp”, Var(“?i”), Const(2) ) as a rule constraint.
in conditional generator	varaible constraints inGeneratorOp	?a: A() in myTerm represented in the constraint part of the rule as Uniterm ( inGeneratorOp, Var(?a), myTerm )
from conditional generator	varaible constraints fromGeneratorOp	?a: A() from myTerm represented in the constraint part of the rule as Uniterm ( fromGeneratorOp, Var(?a), myTerm )
Ruleset name	Extending core meta model	We add an attribute in the Ruleset class.
right statement	Atomic	Only one statement in the right part (Horn clause)
ruleset properties	not supported
rule properties	not supported	Is the priority important for MISMO rules?