TransformationRuleParser.java

package sushi.transformation;

import java.io.Serializable;
import java.util.Map;

import sushi.event.collection.SushiTreeElement;
import sushi.transformation.collection.SushiPatternTree;
import sushi.transformation.element.externalknowledge.ExternalKnowledgeExpressionSet;

/**
 * Provides methods to parse queries in EPL language from a transformation rule.
 */
public abstract class TransformationRuleParser {
	
	/**
	 * Parses an EPL query from the given parameters.
	 * 
	 * @param attributeIdentifiersAndExpressions pairs of attribute identifiers and expressions - determines what values are stored in the transformed events
	 * @param patternTree pattern that is used to listen for events, built up from the provided elements
	 * @return EPL query
	 */
	public abstract String parseRule(SushiPatternTree patternTree, Map<String, String> attributeIdentifiersAndExpressions, Map<String, ExternalKnowledgeExpressionSet> attributeIdentifiersAndExpressionSets);
	
	/**
	 * Parses the pattern part of an EPL query.
	 * 
	 * @param element root element of the pattern tree
	 * @return pattern part of EPL query
	 */
	protected abstract String buildPatternString(SushiTreeElement<Serializable> element);
	
	/**
	 * Parses the value selection part of an EPL query.
	 * 
	 * @param attributeIdentifiersAndExpressions pairs of attribute identifiers and expressions - determines what values are stored in the transformed events
	 * @param attributeIdentifiersAndExpressionSets pairs of attribute identifiers and sets of expressions determining the fetch of external knowledge
	 * @return value selection part of EPL query
	 */
	protected abstract String buildValueSelectionString(Map<String, String> attributeIdentifiersAndExpressions, Map<String, ExternalKnowledgeExpressionSet> attributeIdentifiersAndExpressionSets);
	
	/**
	 * Parses the external knowledge information for the value selection part of an EPL query.
	 * 
	 * @param externalKnowledge sets of expressions determining the fetch of external knowledge
	 * @return external knowledge information part of value selection part of EPL query
	 */
	protected abstract String buildValueSelectionStringFromExternalKnowledge(ExternalKnowledgeExpressionSet externalKnowledge);
}