LexEVS Code Decoupling

Goal

Recommendation

Approach

Design

In order to remove the Lucene references from the LexEVS core code base, we will design a new search API interface.  We would then be able to create a specific Lucene implementation of this interface.  If there was ever a need to substitute different search engine, all that would be necessary would be to create a new implementation of the search API interface for the new search engine.  The LexEVS core code base would not be needed to be modified.

There are several classes that will need to evaluated when doing the actual implementation.  These cases include code where Lucene objects are intermixed throughout LexEVS methods. (This is not an all inclusive list)

This is one example of how an interface could be created to remove Lucene objects from the LexEVS core codebase.  These methods can be pushed into an implementation of the Query interface below.  The interface would be used instead of calling Lucene directly.

//code decoupling

// Interface for creating Queries
public interface Query {

	// methods required for CodedNodeSetImpl 
	public  Query getCodingSchemeQuery(String uri, String internalVersionString);  
	public  Query getRestrictionQuery(Restriction restriction, String internalCodeSystemName, String internalVersionString);  

	// methods required for AbstractLazyCodeHolderFactory
	private  Query getBooleanQuery(List<Query> queries);
	public Query getFilteredQuery(List<Filter> filters, BooleanQuery combinedQuery, Filter chainedFilter);
}

// Lucene Implementation
public class LuceneQuery implements Query {

}

This is another example of an Interface for a ScoreDoc Factory.  AbstractLazyCodeHolderFactory.buildCodeHolder is currently using ScoreDocs.

public interface ScoreDocFactory {

     List<ScoreDoc> getScoreDocs (EntityIndexService service, AbsoluteCodingSchemeVersionReference ref, List<BooleanQuery> combinedQuery,List<Query> bitSetQueries);
}

Different types of Queries and Filter types will need to be defined as well.  We could create an abstract class for each of them.  CodedNodeSetImpl and AbstractLazyCodeHolderFactory will not need to reference Lucene objects directly then.

// Potential abstract classes for defining different types of Lucene objects in a generic manner.
public abstract class QueryType {
}

public abstract class FilterType {
}

public abstract class FilteredQuery {
}