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New Alignment API 4.10. Get it!

Alignment API and Alignment Server

The Alignment API is an API and implementation for expressing and sharing ontology alignments.

Using ontologies is the priviledged way to achieve interoperability among heterogeneous systems within the Semantic web. However, as the ontologies underlying two systems are not necessarily compatible, they may in turn need to be reconcilied. Ontology reconciliation requires most of the time to find the correspondences between entities (e.g., classes, objects, properties) occuring in the ontologies. We call a set of such correspondences an alignment. We have designed a format for expressing alignments in a uniform way. The goal of this format is to be able to share on the web the available alignments. The format is expressed in RDF, so it is freely extensible.

The Alignment API itself is a Java description of tools for accessing the common format. It defines five main interfaces (OntologyNetworks, Alignment, Cell, Relation and Evaluator) and proposes the following services:

Here is the Alignment API and implementation homepage. It is hosted at gitlab.inria.fr.

If you use this software and want to give it credit, please cite:
Jérôme David, Jérôme Euzenat, François Scharffe, Cássia Trojahn dos Santos, The Alignment API 4.0, Semantic web journal 2(1):3-10, 2011

If you have written an extension/patch of the API that you think may be beneficial for other users, do not hesitate to submit it to us before you forget.

Please note: The Alignment API is... an API (this may be unfortunate, but it has been named appropriately). Hence, it is not a matcher. A few examples of trivial matchers are provided with the Alignment API which will indeed match ontologies. Taking such examples, which can be programmed in a couple of hours, as real matchers and comparing this with other matchers is meaningless (only when these matchers are worse than that, this is a meaningful result). Moreover, mentioning that these systems have been compared with "The Alignment API" without qualification is not appropriate. So please, compare your systems with serious competitors (hint: those which publish papers telling that their systems are good matchers; you cannot find such a paper about the Alignment API or one of its sample matcher).

Practical resources

Releases and Release notes
Official releases.
Install & use
Quick start with the API.
Using the Alignment API through command line, web interface, Java programming and advanced programming, and generating links from alignments.
Extending the API and offering alignment server services.
Alignment Server
Installing a server that will generate and store alignments

Technical documentation

Alignment format and the Expressive and Declarative Ontology Alignment Language (EDOAL)
How to express alignments that the API can input or output.
API structure, algebraic operations, our implementation, and its command-line interface
Getting around the API
Alignment server architecture and message specification (REST and SOAP)
Storing and sharing alignments
Wrapping ontology APIs
The package contains an ontology API wrapper called ontowrap allowing for using the Alignment API with various ontology APIs (JENA, OWL API 1.0, 3.0, SKOS API and our SKOSLite API).
Wordnet extension
How to use wordnet within the API
Registered annotations
List of extension labels that are declared (and should not be used by others)
Generating tests and evaluating results
Using the API for evaluating alignments and matchers.

Additional resources

Bug and feature trackers
Notify your bugs and request features here
Git access
You can browse and you can join.
Included libraries and dependencies and a small step towards Maven
Wonderful components that the Alignement API and server use.
Basically, open source (LGPL).
When it is due.
Systems using the API
Because we are proud to be used.


NeOn Alignment plug-in
Alignment API and server plug-in for the NeOn toolkit.
Stripped down Alignment API and implementation for Android.

External resources

The Ontology Alignment Evaluation Initiative: Benchmarks for evaluating ontology matchers and benchmarking campaigns (since 2004).
The central resource for ontology matching and alignment information.