Falcon-AO, a prominent component of Falcon, is an automatic ontology matching system that helps actualize interoperability between (Semantic) Web applications that use different but related ontologies. Recently, it has become a very practical and popular choice for matching Web ontologies expressed by RDF(S) and OWL. Falcon-AO is implemented in Java, and presently, it is an open source project under the Apache 2.0 license.

For the finder part I have implemented a SPARQL backend, which internally delegates to Sesame2, which is the same default index/query that is used to find Entities in general. This in itself is pretty cool, because it means that you can write your domain model in Java, have it be automatically persisted in a store like Neo4j, and then with no extra effort expose it through SPARQL for AJAX webapps to consume (both RDF/XML and JSON output is supported today). Minimally writing a domain model only involves writing Java interfaces (no classes), so it's pretty easy to get started.