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JPMML-Evaluator Build Status

Java Evaluator API for Predictive Model Markup Language (PMML).

Features

JPMML-Evaluator is de facto the reference implementation of the PMML specification versions 3.0, 3.1, 3.2, 4.0, 4.1 and 4.2 for the Java platform:

  1. Pre-processing of active fields according to the [DataDictionary] (http://www.dmg.org/v4-2-1/DataDictionary.html) and [MiningSchema] (http://www.dmg.org/v4-2-1/MiningSchema.html) elements:
  • Complete data type system.
  • Complete operational type system.
  • Treatment of outlier, missing and/or invalid values.
  1. Model evaluation:
  1. Post-processing of target fields according to the [Targets] (http://www.dmg.org/v4-2-1/Targets.html) element:
  • Rescaling and/or casting regression results.
  • Replacing a missing regression result with the default value.
  • Replacing a missing classification result with the map of prior probabilities.
  1. Calculation of auxiliary output fields according to the [Output] (http://www.dmg.org/v4-2-1/Output.html) element:
  • Over 20 different result feature types.
  1. Model verification according to the [ModelVerification] (http://www.dmg.org/v4-2-1/ModelVerification.html) element.

For more information please see the [features.md] (https://github.com/jpmml/jpmml-evaluator/blob/master/features.md) file.

JPMML-Evaluator is interoperable with most popular statistics and data mining software:

JPMML-Evaluator is fast and memory efficient. It can deliver one million scorings per second already on a desktop computer.

Prerequisites

  • Java 1.7 or newer.

Installation

JPMML-Evaluator library JAR files (together with accompanying Java source and Javadocs JAR files) are released via [Maven Central Repository] (http://repo1.maven.org/maven2/org/jpmml/).

The current version is 1.2.13 (20 March, 2016).

<dependency>
	<groupId>org.jpmml</groupId>
	<artifactId>pmml-evaluator</artifactId>
	<version>1.2.13</version>
</dependency>

Usage

Loading models

JPMML-Evaluator depends on the [JPMML-Model] (https://github.com/jpmml/jpmml-model) library for PMML class model.

Loading a PMML schema version 3.X or 4.X document into an org.dmg.pmml.PMML instance:

PMML pmml;

try(InputStream is = ...){
	Source transformedSource = ImportFilter.apply(new InputSource(is));

	pmml = JAXBUtil.unmarshalPMML(transformedSource);
}

If the model type is known, then it is possible to instantiate the corresponding subclass of org.jpmml.evaluator.ModelEvaluator directly:

PMML pmml = ...;

ModelEvaluator<TreeModel> modelEvaluator = new TreeModelEvaluator(pmml);

Otherwise, if the model type is unknown, then the model evaluator instantiation work should be delegated to an instance of class org.jpmml.evaluator.ModelEvaluatorFactory:

PMML pmml = ...;

ModelEvaluatorFactory modelEvaluatorFactory = ModelEvaluatorFactory.newInstance();
 
ModelEvaluator<?> modelEvaluator = modelEvaluatorFactory.newModelManager(pmml);

Model evaluator classes follow functional programming principles and are completely thread safe.

Model evaluator instances are fairly lightweight, which makes them cheap to create and destroy. Nevertheless, long-running applications should maintain a one-to-one mapping between PMML and ModelEvaluator instances for better performance.

It is advisable for application code to work against the org.jpmml.evaluator.Evaluator interface:

Evaluator evaluator = (Evaluator)modelEvaluator;

Querying the "data schema" of models

The model evaluator can be queried for the list of active (ie. independent), target (ie. primary dependent) and output (ie. secondary dependent) field names. Field names can be resolved to field definitions, which provide data type, operational type, value domain etc. information.

Querying and parsing active fields:

List<FieldName> activeFields = evaluator.getActiveFields();

for(FieldName activeField : activeFields){
	MiningField miningField = evaluator.getMiningField(activeField);
	DataField dataField = evaluator.getDataField(activeField);

	DataType dataType = dataField.getDataType();

	OpType opType = dataField.getOpType();
	switch(opType){
		case CONTINUOUS:
			RangeSet<Double> validArgumentRanges = FieldValueUtil.getValidRanges(dataField);
			break;
		case CATEGORICAL:
		case ORDINAL:
			List<Value> validArgumentValues = FieldValueUtil.getValidValues(dataField);
			break;
		default:
			break;
	}
}

Querying and parsing target fields:

List<FieldName> targetFields = EvaluatorUtil.getTargetFields(evaluator);

for(FieldName targetField : targetFields){
	MiningField miningField = evaluator.getMiningField(targetField);
	DataField dataField = evaluator.getDataField(targetField);
	Target target = evaluator.getTarget(targetField);

	DataType dataType = dataField.getDataType();

	OpType opType = dataField.getOpType();

	// The MiningField element overrides the DataField element
	if(miningField != null && miningField.getOpType() != null){
		opType = miningField.getOpType();
	} // End if

	// The Target element overrides the MiningField element
	if(target != null && target.getOpType() != null){
		opType = target.getOpType();
	}

	switch(opType){
		case CONTINUOUS:
			break;
		case CATEGORICAL:
		case ORDINAL:
			List<Value> validResultValues = FieldValueUtil.getValidValues(dataField);
			break;
		default:
			break;
	}
}

The method EvaluatorUtil#getTargetFields(Evaluator) is a "safe" wrapper for the Evaluator#getTargetFields() method.

Querying and parsing output fields:

List<FieldName> outputFields = EvaluatorUtil.getOutputFields(evaluator);

for(FieldName outputField : outputFields){
	OutputField output = EvaluatorUtil.getOutputField(evaluator, outputField);

	DataType dataType = output.getDataType();

	OpType opType = output.getOpType();
}

Methods EvaluatorUtil#getOutputFields(Evaluator) and EvaluatorUtil#getOutputField(Evaluator, FieldName) are "safe" wrappers for methods Evaluator#getOutputFields() and Evaluator#getOutputField(FieldName), respectively.

Evaluating models

The PMML scoring operation must be invoked with valid arguments. Otherwise, the behaviour of the model evaluator class is unspecified.

Preparing a data record:

Map<FieldName, FieldValue> arguments = new LinkedHashMap<>();

List<FieldName> activeFields = evaluator.getActiveFields();
for(FieldName activeField : activeFields){
	// The raw (ie. user-supplied) value could be any Java primitive value
	Object rawValue = ...;

	// The raw value is passed through: 1) outlier treatment, 2) missing value treatment, 3) invalid value treatment and 4) type conversion
	FieldValue activeValue = evaluator.prepare(activeField, rawValue);

	arguments.put(activeField, activeValue);
}

Evaluating the data record:

Map<FieldName, ?> results = evaluator.evaluate(arguments);

Typically, a model has exactly one target field:

FieldName targetName = evaluator.getTargetField();

Object targetValue = results.get(targetName);

The target value is either a Java primitive value (as a wrapper object) or an instance of org.jpmml.evaluator.Computable:

if(targetValue instanceof Computable){
	Computable computable = (Computable)targetValue;

	Object primitiveValue = computable.getResult();
}

The target value may implement interfaces that descend from interface org.jpmml.evaluator.ResultFeature:

// Test for "entityId" result feature
if(targetValue instanceof HasEntityId){
	HasEntityId hasEntityId = (HasEntityId)targetValue;
	HasEntityRegistry<?> hasEntityRegistry = (HasEntityRegistry<?>)evaluator;
	BiMap<String, ? extends Entity> entities = hasEntityRegistry.getEntityRegistry();
	Entity winner = entities.get(hasEntityId.getEntityId());

	// Test for "probability" result feature
	if(targetValue instanceof HasProbability){
		HasProbability hasProbability = (HasProbability)targetValue;
		Double winnerProbability = hasProbability.getProbability(winner.getId());
	}
}

Example applications

Module pmml-evaluator-example exemplifies the use of the JPMML-Evaluator library.

This module can be built using [Apache Maven] (http://maven.apache.org/):

mvn clean install

The resulting uber-JAR file target/example-1.2-SNAPSHOT.jar contains the following command-line applications:

Evaluating model model.pmml by loading input data records from input.tsv and storing output data records to output.tsv:

java -cp target/example-1.2-SNAPSHOT.jar org.jpmml.evaluator.EvaluationExample --model model.pmml --input input.tsv --output output.tsv

Getting help:

java -cp target/example-1.2-SNAPSHOT.jar org.jpmml.evaluator.EvaluationExample --help

Documentation

The [Openscoring.io blog] (http://openscoring.io/blog/) contains fully worked out examples about using JPMML-Model and JPMML-Evaluator libraries.

Recommended reading:

Please join the [JPMML mailing list] (https://groups.google.com/forum/#!forum/jpmml) for technical discussion.

License

JPMML-Evaluator is licensed under the [GNU Affero General Public License (AGPL) version 3.0] (http://www.gnu.org/licenses/agpl-3.0.html). Other licenses are available on request.

Additional information

Please contact [[email protected]] (mailto:[email protected])

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Java Evaluator API for PMML

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