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4.5 Exercises 87

Summary

• OWL is based on RDF and has three increasingly more general levels:
  OWL Lite, OWL-DL, and OWL Full.


• An OWL document defines a theory of the world. States of the world that
  are consistent with the theory are called models of the theory.


• A fact that is true in every model is said to be entailed by the theory. OWL
  inference is defined by entailment.


• OWL is especially well suited for defining concepts in terms of other con-
  cepts using class constructors.


• OWL has only one property constructor, but it has some property con-
  straints.


• Resources can be explicitly stated to be the same or different. It is also
  possible to infer that two resources are the same or different.


• To perform inference in OWL one must focus on a particular question.


• OWL inference is monotonic, which can limit inferences, but careful de-
  sign can reduce this problem.

4.5 Exercises

1. Restate the molecule schema in figure 1.6 as an RDF ontology. There will
   not be a single correct answer to this exercise.


2. Define the nitrous oxide molecule in figure 2.3 using RDF. The answer will
   depend on the RDF ontology.


3. Rewrite the bio sequence DTD in exercise 4.2 as an OWL ontology.


4. Rewrite the physical units DTD in exercise 4.3 as an OWL ontology.


5. Rewrite the Fitzhugh-Nagumo model and DTD in exercise 4.4 as an OWL
   ontology.