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School of Information Engineering Knowledge Engineering 2011–12 Solutions of Test 3 – 10 th September 2012 1 8 pt. Explain what is, in your opinion, the main difference between a database and a knowledge base. Describe the difference conceptually, explaining the key technical notions, and complement your description with a meaningful example. The main difference is that in a knowledge base (KB) the conceptual model is represented explicitly and is available for generating answers to queries. In KBs based on a Description Logic (DL), like for example OWL 2 DL, the conceptual model is represented as a set of axioms. Queries are regarded as statements that may be proved as theorems by reasoning, starting from such axioms. As an example, suppose that a conceptual model speci fies that every person has exactly two parents, and that the data specify that Mary is a parent of John. Then the query to a KB, “Does John have two parents?” would give answer “ yes” because this can be derived from the conceptual model. No such answer can be produced by a traditional database. 2 14 pt. Translate the requirements below into OWL 2 DL, using the DL notation. Specify the domain and range of every property. In case a requirement cannot be specified in OWL 2 DL explain why, and if possible provide an OWL 2 DL approximation. Avoid redundancies (i.e., do not state again what can be derived from existing axioms) and use ABox assertions whenever possible. 1. every town belongs to exactly one country; 2. every country has exactly one town as its capital; 3. the capital of a country belongs to that country; 4. two countries may be neighbouring; if country x is a neighbour of country y, then y is a neighbour of x; 5. no country neighbours with itself; 6. if a country has no neighbouring…