This book is the first textbook for an introduction in ontology engineering. Indeed, there are books about ontology engineering, but they either promote one specific ontology or methodology only, are handbooks, or are conference proceedings. The intended audience for this textbook are people at the level of advanced undergraduate and early postgraduate studies in computer science. This entails, for instance, that I assume the reader will know what UML class diagrams and databases are.
- This chapter introduces ontologies: what they are (roughly), what they are used for, and describes a few success stories where they have been instrumental at solving problems. Where and how an ontology can solve problems is not of the variety “when you have only a hammer, everything looks like a nail”, but where the use of an ontology was the solution to a particular problem, or at least an essential ingredient of it.
- Perhaps more foundations in modelling may be useful before delving into how to represent what you want to represent, but at the same time, one also needs to understand the language to model in. In this case, this means obtaining a basic grasp of logic-based ontology languages, which will help understanding the ontologies and ontology engineering better, and how to formalise the things one wants to represent.
- A Description Logic (DL) is a structured fragment of FOL; more precisely: any (basic) Description Logic language is a subset of L3 , i.e., the function-free FOL using only at most three variable names. Its representation is at the predicate level: no variables are present in the formalism. DLs provide a logical reconstruction and (claimed to be a) unifying formalism for other knowledge representation languages, such as frames-based systems, object-oriented modelling, Semantic data models, etc.
- In the previous two chapters we have seen first FOL and then a version of it that was slightly changed with respect to notation and number of features in the language (easier, and less, respectively), being the DL family of languages. They haven’t gotten us anywhere close to implementations, however. This is set to change in this chapter, where we will look at ‘implementation versions’ of DLs that have rich tooling support.
- The main aim of this chapter is to provide several pointers to more advanced language features that allow the modeller to represent more than can be done with the DL-based OWL species only. We shall see some solutions to earlier-mentioned modelling question, among others: with which extension that “small” of the ‘small bladed hunting spear’ can be represented and how the essential and immutable behaviour of the parthood relation with the boxer and his hands vs. brain and human is resolved.