Necessary classes to implement query builders.
The namespace Lucene.Net.QueryParsers.Core.Builders contains the interface that builders must implement, it also contain a utility xref:Lucene.Net.QueryParsers.Flexible.Core.Builders.QueryTreeBuilder, which walks the tree and call the Builder for each node in the tree. Builder normally convert QueryNode Object into a Lucene Query Object, and normally it's a one-to-one mapping class. But other builders implementations can by written to convert QueryNode objects to other non-Lucene objects.