The ontology projection descriptor

The projection is represented in an XML document, conforming to the schema associated to the namespace http://semanticturkey.uniroma2.it/extensions/uimast/schemas/projection-20081117#.

Even if there isn't a projection editor, any XML editor can provide a great help (template generation, autocompletion, validation, etc...), once the schema has been added to its Catalog.

The overall projection should look as the following.

<!DOCTYPE projection[          <!ENTITY proj "http://semanticturkey.uniroma2.it/extensions/uimast/schemas/projection-20081117#">          <!ENTITY base "ontology default namespace">  ]> <projection xmlns="&proj;">         <typesystem location="type system URI" />          <annotation type="a type" mode="xpointer">                           </annotation>          <project class="source class" into="target type">                           </project> </projection>

It is advisable to define in the DTD internal subset two entities, which may be used later to shorten the URIs employed in the projection.

The entity proj expands to the projection namespace URI, while the entity base should expand to the ontology default namespace (a symbol Foo in the default namespace may be identified by the URI &base;Foo).

The mandatory element typesystem specifies the type system location either by absolute or relative (wrt the projection descriptor) file URI.

The mandatory element annotation sets the annotation base type, which holds the regional reference. The attribute mode customizes the export mechanism: at the present it must have the value xpointer meaning that the regional reference is an XPointer expression.

The feature initializers within the annotation element intialize the features of that type.

There must be zero or more project element to project an ontology class into a type.

The attribute class specifies the URI of the source class and the attribute into is the fully qualified name of the target type.

The feature initializers within the project element intialize the features of the target type.

The schema can enforce that a class isn't projected more than once and that a feature isn't initialized twice in a given context.

It cannot express the constraint that given two classes A, B and their associated types T(A), T(B), if A rdf:subClassOf B then T(A) extends or is equal to T(B).

A feature initializer should look like the following.

<feature name="feature name" value="a literal value" property="a property" />

The attribute name is the short name of the feature to be initialized.

The attribute property is the URI of a property to be used to initialize the feature. When the data are projected, the property is resolved against the current domain object.

The attribute value is a literal representation (according to the XML Schema standard) of the value to be assigned to the feature.

The schema isn't able to express the following constraints:

the feature must belong to the bounding type

the property range must be compatible either with the feature range or its element type (if it is an array feature)

xsd:boolean	uima.cas.Boolean
xsd:byte	uima.cas.Byte
xsd:short	uima.cas.Short
xsd:int	uima.cas.Integer
xsd:long	uima.cas.Long
xsd:float	uima.cas.Float
xsd:double	uima.cas.Double
xsd:string	uima.cas.String
xsd:string	enumerated type

In the last case each property value must be checked, to ensure that it is allowed. Indeed, at the present Semantic Turkey doesn't let the user restrict a property range to a given set of values.

the attribute value and property are mutually exclusive

In the context of the element annotation the user must initialize the annotation base type with the regional reference of the current annotation.

It may be accessed through the wired property &proj;range, which evaluates to the XPointer expression associated with the current annotation.

The wired property &proj;identity evaluates to the URI identifying the current domain object.

Example projection

There is a sample projection in the downloads section of UIMAST project site. It is composed of the following files:

sample_ont.owl: a simple ontology containing annotations taken about three academic researchers and the university they work in. The ontology imports the ST sample ontology: http://art.uniroma2.it/ontologies/st_example and reuses some of its concepts. In particular, it extends the concept stx:Person with two subconcepts: Professor and Researcher, which are used to typize the annotated individuals.
stx-mine_typesystem.xml: a type system, containing the definition of UIMA type: XPointerAnnotation, which is the base type for annotations accepted by UIMAST. It also contains the type: Persona (Person), and a feature: lavoro (job) describing the kind of position of people, and pointing to the UIMA type: Occupazione (Position), which accepts two values: professore (professor) and ricercatore (researcher).
stx-mine_projection.xml: this projection file contains rules for projecting all the stx:Person subclasses in the sample ontology to the UIMA type Persona. In particular, class Professor is projected over the UIMA type Persona with the lavoro feature set to professore, while class Researcher is projected over the UIMA type Researcher with the lavoro feature set to researcher