Jean Vincent Fonou Dombeu and Magda Huisman
the RDF version of the domain ontology is created with Jena API( step 2 in Figure 2) and saved persistently with the MySQL RDBMS( step 3 in Figure 2). Finally, SPARQL queries are written to query the RDF store of the domain ontology( step 4 in Figure 2). The next subsections describe the abovementioned steps in detail.
Figure 1: Domain ontology for e‐Government monitoring of development projects in developing countries
5.2 Semi‐formal representation of the domain ontology in description logic
The ontology engineering field prescribes three layers of ontology development according to the formalisms used( Uschold and King 1995). From a form that can be understood by human beings to one that can be processed by computers, these ontology layers are: informal ontology( as in Figure 1), semi‐formal ontology and formal ontology( Uschold and King 1995). Two formalisms are commonly used to represent a semi‐formal ontology; they include Unified Modelling Language( UML) class diagram( Ceccaroni and Kendall 2003) and description logic( Fahad et al. 2008; Baader and Horrocks 2005; Pan 2007). In this research, the description logic formalism is used. Description Logic is a formal language for knowledge representation. Its syntax uses basic mathematical logic symbols such as subset, union, intersection, universal and existential quantifications, etc. to represent the relationships between the constituents of a domain. The description logic version of the domain ontology in Figure 1 is obtained by analysing its semantic and logical structures, identifying its classes, class hierarchy and class instances, and defining relationships between classes.
The relationships include inheritance and association / composition relationships. A relationship is also called property or slot. Thereafter, the mathematical logic symbols mentioned above are used to represent the class hierarchy, relationships between classes( inheritance and properties), constraints on properties, etc. For instance, in the class hierarchy of the domain ontology( Figure 1), community worker, community leader, traditional leader, and project staff are people( person class) involved in the development project implementation. Therefore, community worker, community leader, traditional leader, and project staff are subclasses of the person class, representing an inheritance relationship. This relationship is represented in description logic formalism using the subset and existential quantification symbols, and the isA property as follows:
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