/*
* Ivory: A Hadoop toolkit for web-scale information retrieval
*
* Licensed under the Apache License, Version 2.0 (the "License"); you
* may not use this file except in compliance with the License. You may
* obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
* implied. See the License for the specific language governing
* permissions and limitations under the License.
*/
package ivory.smrf.model.builder;
import java.io.IOException;
import ivory.cascade.model.builder.CascadeFeatureBasedMRFBuilder;
import ivory.core.RetrievalEnvironment;
import ivory.core.exception.ConfigurationException;
import ivory.core.exception.RetrievalException;
import ivory.core.util.XMLTools;
import ivory.smrf.model.MarkovRandomField;
import ivory.smrf.model.constrained.GreedyConstrainedMRFBuilder;
import org.w3c.dom.Node;
import com.google.common.base.Preconditions;
/**
* @author Don Metzler
*/
public abstract class MRFBuilder {
protected final RetrievalEnvironment env;
public MRFBuilder(RetrievalEnvironment env) {
this.env = Preconditions.checkNotNull(env);
}
public abstract MarkovRandomField buildMRF(String[] queryTerms) throws ConfigurationException;
public static MRFBuilder get(RetrievalEnvironment env, Node model) throws ConfigurationException {
Preconditions.checkNotNull(env);
Preconditions.checkNotNull(model);
// Get model type.
String modelType = XMLTools.getAttributeValueOrThrowException(model, "type",
"Model type must be specified!");
// Build the builder.
MRFBuilder builder = null;
try {
if ("Feature".equals(modelType)) {
builder = new FeatureBasedMRFBuilder(env, model);
} else if ("GreedyConstrained".equals(modelType)) {
builder = new GreedyConstrainedMRFBuilder(env, model);
} else if (modelType.equals("New")) {
builder = new CascadeFeatureBasedMRFBuilder(env, model);
} else {
throw new ConfigurationException("Unrecognized model type: " + modelType);
}
} catch (IOException e) {
throw new RetrievalException("Error getting MRFBuilder: " + e);
}
return builder;
}
}