The Use of UML as a Tool for the Formalisation of Standards and the Design of Ontologies in Agriculture

For the past 20 years, ontologies have become more and more popular in various research fields such as Web technologies, databases, information retrieval methods, and so forth. The first goal of this chapter is to answer general questions about ontologies, such as: What exactly is an ontology? What is the purpose of ontology? Which types of systems use an ontology? The second goal of the chapter is to help readers understand how UML can be used to model ontologies in agricultural systems. UML and the Web Ontology Language (OWL) are compared, and an example inspired by the French project named Farm Information Management is presented. 1 What Is an Ontology? This section will briefly describe the history of the word ontology starting from Aristotle’s metaphysics to the more sophisticated Web technologies. Thus, readers will be able to gain a rapid overview of the use of ontologies in different domains. Then we will conclude by giving a general definition of ontologies. Aristotle’s definition of the wordOntology (with a capitalO) is ‘‘the science of being qua being’’ (Aristotle’s Metaphysics). This science is part of philosophy, dealing with the descriptions of existing entities. Its goal is to define the general categories or primitives used to classify all the entities in the world such as human beings, animals, plants, and so forth. In the early 1980 s, artificial intelligence researchers borrowed the term Ontology from the field of philosophy. Ontologies became the definition of domain knowledge. They provide the possibility to separate domain knowledge from operational knowledge [29]. F. Pinet (*) Cemagref, Clermont Ferrand, France e-mail: [email protected] P.J. Papajorgji, P.M. Pardalos (eds.), Advances in Modeling Agricultural Systems, DOI 10.1007/978-0-387-75181-8_7, Springer ScienceþBusiness Media, LLC 2009 131 An interesting definition of ontologies in the field of artificial intelligence was proposed by Gruber in 1993: an ontology is ‘‘the specification of conceptualisations used to help programs and humans share knowledge’’ [13]. He developed a more precise definition: ‘‘. . .ontology is a formal explicit specification of a shared conceptualization.’’ According to Gruber, conceptualisation refers to an abstract model of phenomena in the world after identifying the relevant concepts of these phenomena. Explicit means that the type of concepts used and the constraints on their use are explicitly defined. Formal refers to the fact that the ontology should be machine readable. Shared reflects the idea that ontology should capture consensual knowledge accepted by the communities [14]. In database and information system areas, ontologies are used to facilitate the interoperability of heterogeneous information sources. The ontology is the general schema organising all the entity properties described in a group of database schemas or information sources. Each information source is provided with a wrapper that maps its database schema to the ontology. Thus, users can query the ontology and obtain a result integrating all information sources needed to answer the query [34]. Information retrieval techniques use linguistic ontology such as indexing vocabulary in order to avoid word semantic ambiguity. Thus, document and query contents are represented by concepts (i.e., the meaning of terms) and not words (i.e., sets of characters). This technique means it is possible to improve the description of document (and query) contents and also system performance. One of the first operational systems was Ontoseek, which uses Wordnet taxonomy to describe yellow pages [15, 20]. The Semantic Web is an adaptation of previous technologies. Tim BernersLee, the inventor of the Web, defines the Semantic Web as ‘‘a web of data that can be processed directly and indirectly by machines.’’ Indeed, the Semantic Web is about several things: the exchange and processing of data, documents, and services. The SemanticWebwill integrate a community of agents capable of exchanging data and services from diverse sources in order to achieve a specific goal. More precisely, such Web services are reusable software components that implement a discrete functionality (like hotel reservation) accessible through theWeb.Moreover, document description and content will be defined precisely thanks to series of data called metadata stored in ontologies. Thus, Web document retrieval is improved by this technique. The W3C 1 is in charge of developing a set of standards necessary for Semantic Web technology [30]. All these standards are based on the ExtensibleMarkup Language (XML) (W3C Semantic Web activity). In the agricultural domain, the well-known AGROVOC thesaurus is used to develop the Agricultural Ontology Service (AOS) project [1]. AGROVOC is a multilingual thesaurus concerning forestry, fisheries, food, environment, and 1 W3C, World Wide Web Consortium; see www.w3c.org. 132 F. Pinet et al.