Searching Annotated Collections: Applications

Despite the great interest in di erent forms of textual annotation (named entity extraction, semantic tagging, syntactic and semantic parsing, etc.), there is still no consensus about which search tasks can be improved with such annotations, and what search algorithms are required to implement e cient engines to solve these tasks. We de ne formally two retrieval tasks in annotated collections: annotated retrieval and element retrieval. We discuss their di erences and describe e cient indexing structures, and how they can be implemented in Lucene and MG4J, two open source retrieval engines. Finally, we give a technical overview of two element retrieval use cases.