Delivery Context Ontology

1.1.1 Disjoint Classes

The ontology contains a large number of disjoint classes. OWL-DL requires explicit definition of each disjoint relationship between classes. The number of such definitions becomes unmanageably large in ontololgies with a large number of classes.

Fortunately, there is an alternative mechanism for ensuring that classes are considered disjoint, without requiring the use of explicit statements. The mechanism relies on each class including a property that has a unique value. In this ontology, the property used is called deliveryContextEntityName. Each class derived from DeliveryContextEntity includes this property. Each class has a unique value for this property. The mechanism is referenced in the OWL Guide[OWL] in the discussion on disjoint classes. An illustration of the technique appears in [OWL-Test] in the section on Positive Entailment Test.

1.2.1 Conformance Information

1.3.1 Reading the Property Tables

Each class in the ontology is associated with a set of properties. These properties are defined in tables in the appropriate section of the specification. Each row in a table defines a single property in terms of a number of fields. The fields used in these tables are described as follows:

Name

This field contains the formal name of the property within the class.

Type

This field contains the type of the property. Datatype properties have types that are not themselves classes. Examples include xsd:int, xsd:boolean, xsd:string and xsd:float. Object properties have types that are classes. Usually these classes are themselves defined in the ontology.

Description

This field contains a description of the property.

Occurs

This field defines the cardinality of the property. The number of occurences of the property within the class is shown as an expression. For example, the expression ≥ 0 and ≤ 1 indicates that a property is optional. It's cardinality is 0 or 1. Similarly, the expression =1 indicates that a property always occurs exactly once.

Value(s)

This field holds values that apply across every instance of a class.

Some property values are fixed for every instance of a class. Where this is the case, the value shown in the Value(s) field is prefixed by the phrase Class Value:. For example, every instance of the class Meters, which represents a physical length in meters, has a unitName property with the value "meter".

Some properties can hold values from a specific, predefined set. Where this is the case, the value shown in the Value(s) field is prefixed by the phrase One of:. For example, the Orientation class, which represents the orientation of features such as displays or cameras, has an orientationValue property which can take only the values 0, 90, 180 or 270.

Alternate Names

This field defines the alternative names for the property. Alternative names might be useful in different programming environments for consistency with conventions.

1.3.2 Reading the Example Tables

Examples are given for specific classes in the specification. The associated tables contain one or more example classes, complete with values for each of their properties. The fields used in these tables are described as follows:

Example Instance

This field contains the identification of the instance that provides the example.

Property Name

This field contains the formal name of the property whose value is shown as part of the example.

Type

This field contains the type of the property in the example. Datatype properties have types that are not themselves classes. Examples include xsd:int, xsd:boolean, xsd:string and xsd:float. Object properties have types that are classes. Usually these classes are themselves defined in the ontology.

Value(s)

This field contains the value(s) of the property. Where a property has a cardinality of >1, multiple values may be shown in the example.