INFS3101/7100
Ontology and the Semantic Web
Semester 1, 2006
Assignment Value
40%
Due Monday, 8 May,
4:00 pm, in assignment box level 1, Building 78
Purpose: Gain an understanding of the main principles of ontology in a practical situation
This assignment is to be done in
groups of up to three. Unless a strong case is made to the contrary, all
students in a group will receive the same mark. (Note that a student may do the
assignment as a group of one, but that no allowance will be made in the marking
for doing so.)
1. Find a published ontology of some kind. No two groups should have the same ontology, so your ontology choice should be registered with the lecturer as soon as possible. It will be published anonymously on the course web site.
2. Identify three distinct players who interoperate using this ontology, and three distinct roles that can be taken in the interoperation. Briefly describe what each role does and how the players interact using the ontology.
Show three concrete actions taken by players as they interoperate. Include details of players and roles involved, and the contents of the messages. (3 marks)
3. Briefly describe the ontology, giving enough detail to understand the elements of the ontology involved in the actions of 2. You should include enough concepts to get an idea of the scope and content of the whole ontology. Include some instances of all classes, including all instances used in the actions of 2. Your description should be supported by a diagram in the representation language of Chapter 4, with between 25 and 50 classes. (5 marks)
4. Describe three institutional facts created in this network, including brute fact and context. What roles are responsible for creation of each fact? Who is responsible for keeping the definitive record of the fact? You may use the actions of 2. (3 marks)
5. Describe two shared complex objects. What are their parts? What are their identifying and unifying relations? (4 marks)
6. Describe a bulk class in the ontology, showing how it satisfies the criteria to be a bulk class. If there is none, propose a plausible addition. (3 marks)
7. Describe the three classes in the ontology from 5 and 6. Give their rigid properties, indicating whether the rigid properties are lexical or logical. Show a system of subclasses for each class, inventing a plausible system if necessary. Each subclass is either defined or declared. If it is defined, give the defining predicates. If it is declared, tell how objects are classified into the subclass and by which role (5 marks)
8. Describe a property (relationship, association) involving at least one of the classes from 7. This property should have a subproperty structure. Invent a plausible structure if necessary. Show a population of property instances, including at least one instance of each subproperty. (3 Marks)
9. Describe in detail two endurants and two perdurants in the ontology. (If there are no perdurants, invent two plausible ones). What endurants participate in the perdurants? How are the histories of the endurants represented in the ontology? (4 marks)
10. Criticise the ontology in terms of the five principles of Gruber (6 marks).
- Clarity: suggest a plausible unintended interpretation of one of the concepts. How does (or could) the ontology prevent that unintended interpretation?
- Coherence: suggest a plausible inference that an agent could be expected to draw from the ontology. How does (or could) the ontology support the reasoning necessary to make the inference?
- Extendibility: suggest a plausible extension to the ontology. Show what changes would need to be made. Are any of the changes redundant? If so, show how. If not, show how the ontology design anticipated the extension.
- Encoding bias: Show how one of the actions of 2 is implemented. Does it make sense for it to be implemented in a different way? If not, why not? If so, does the ontology make the different implementation difficult? Consider each element of the implementation of the action.
- Ontological commitment: Describe the particular system of interoperations the ontology is intended to be used for (this could be a class of systems, with multiple separate instances). Is there a different system of interoperations in which the ontology could be reused? If so briefly describe the different system and how the ontology could be adapted to the re-use. If not, why are there no similar systems?
- In each quality dimension, indicate whether in your judgment the quality is high or low.
11. Propose an improvement to the ontology. Argue why this improvement is a good idea in terms of at least one of GruberŐs principles. Show a cost of the change. On balance, is the improvement a good idea? Take a position and justify it. (4 marks)
Note: The object of the exercise is to demonstrate your understanding of the concepts and principles of ontology as contained in the course material. Since engagement with the detail is essential for understanding, descriptions should be detailed enough to see what is going on. For example a simple create(object) is not sufficient. The description should include under what conditions the create is possible, who sends the message to whom, and what information is contained in the message.