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= The AlignmentOntology (AO) =

The AlignmentOntology aims for a formalisation of the concept of an alignment and the relations it is based on. It is defined by an [repos:trunk/PhaseLibs/AlignmentOntology/alignment.rdfs RDFSchema file]. A corresponding [repos:trunk/PhaseLibs/AlignmentOntology/alignment.pprj Protégé 3.1.1 project] is also available. Be aware that this ontology is '''under development''' and may be '''subject to changes'''.

== News ==

 * [04.07.06] '''EXTENSION:''' [mailto:horak@dfki.uni-kl.de Benjamin Horak] added DiscreteAttachments and Acknowledgements.
 * [04.07.06] '''CHANGE:''' Retyped the xsd:anyURI datatype references to the ontology entities. rdf:resource is better.
 * [30.06.06] The first version of an [wiki:AOPorter im-/exporter tool] is now available, allowing to export PhaseLibs alignments to an AO rdf file, and to import such a file by an PhaseLibs alignment implementation.
 * [29.06.06] The AO has been created by [mailto:horak@dfki.uni-kl.de Benjamin Horak] and [mailto:endres@dfki.uni-kl.de Björn Endres]. The draft is now subject to discussion.

== Feature/Change Requests ==

not yet


== License Issues ==

The Alignment Ontology is published under the [http://www.gnu.org/licenses/lgpl.html GNU Lesser General Public License (LGPL)]. 

== Integration/Alignment with other alignment ontologies ==

=== Lockheed Martin Alignment ===
An alignment between our AlignmentOntology and the [http://www.atl.lmco.com/projects/ontology/ Lockheed Martin ATL] [http://www.atl.lmco.com/projects/ontology/ontologies/core/alignment/Alignment.owl alignment specification] is given by the file [repos:trunk/PhaseLibs/AlignmentOntology/LMCOAlignment.rdf LMCOAlignment.rdf]. This file specifies the alignment using both schemes at the same time.

=== SKOS Mapping ===
The [http://www.w3.org/2004/02/skos/mapping/spec/ SKOS Mapping Vocabulary] defines mappings between topic maps. However, their scheme is not semantically equivalent to our alignment concept, since they use a set theory based approach on the documents attached to their concepts. Thus, the transformation of a SKOS mapping into a PhaseLibs alignment or vice versa is semantically questionable.

In order to transform a set of simple (one-to-many) SKOS mappings you can do the following:
 * the various degrees of matches can be mapped to the confidence property 
 * flat AND bag constructs can be transformed to refer instead to an artificial subclasse of the given class conjunction.  
 * flat OR bag constructs can be expressed by a number of Superordination/Subsumption relations.
 * NOT constructs can be expressed by a number of Distinctions.

== Ontology Description ==

The AlignmentOntology basically defines relations between ontology entities, e.g. classes, properties, instances. The semantic of a basic, untyped relation is a connection of any kind, a cooccurrence. There are also further specifications of a realtion:
 * '''Subsumption''' defines a relation like subclass_of or subproperty_of
 * '''Superordination''' is the opposite of Subsumption
 * '''Equivalence''' defines the two entities as semantically equivalent. In particular, this is the case if it is a supsumtion AND a superordination at the same time.
 * '''Classification''' defines a type_of relationship, e.g. that an instance belongs to a class.
 * '''Distinction''' states, that neither of the above holds for the relation

[[Image(relationTypes.gif, 679px, align=center, The different Relation Types)]]

Each relation defines
 * the two entities to relate
 * a confidence value which expresses the confidence that the producer has of the correctness of the relation
 * an arbitrary number of attachments, that supply additional information but are formally not important.

Finally, an Alignment is defined as a set of such Relations. Since the consistency of an alignment is controversial, this is not taken care of here. Further specialisations of Alignment will adress such issues.

[[Image(alignmentStructure.gif, 305px, The Alignment)]]  

In order to store additional information with the Relations, an RelationAttachment resource can be provided. A subtype, the DiscreteRelationAttachment, additionally defines a backlink to the relation resource being attached to, as well as an optional creator property. The following types of attachments have been included so far:
 * '''Similarity''' - Describes the type and value of a similarity, that has led to the creation of this Relation.
 * '''Acknowledgement''' - Describes an external review of the Relation, e.g. user confirmation.

[[Image(attachmentTypes.gif, 305px, The Alignment)]]