08: OWL continued

Question 1

The W3C Web Ontology Language (OWL) is a ___ ___ language designed to represent ____ and ____ knowledge about ____, groups of ____, and ____ between ____.

Answer 1

The W3C Web Ontology Language (OWL) is a semantic** **web** language designed to represent **rich** and **complex knowledge about things, groups of things, and relations between things.

Question 2

OWL is a ____ ____-based language such that knowledge expressed in OWL can be ____ by computer programs, e.g. verify the ____ consistency of that knowledge or to make important knowledge explicit.

Answer 2

OWL is a computational** **logic**-based language such that knowledge expressed in OWL can be **exploited** by computer programs, e.g. **verify the consistency of that knowledge or to make important knowledge explicit.

Question 3

OWL documents, known as ____, can be published in the World Wide Web and may refer to or be referred from other ____ ____.

Answer 3

OWL documents, known as ontologies, can be published in the World Wide Web and may refer to or be referred from other OWL** **ontologies.

Question 4

OWL is part of the W3C’s Semantic Web ____ ____, which includes RDF, RDFS, SPARQL, etc.

Answer 4

OWL is part of the W3C’s Semantic Web technology stack, which includes RDF, RDFS, SPARQL, etc.

Question 5

OWL 2 is an ____ and ____ of the 2004 version of OWL developed by the W3C Web Ontology Working Group.

Answer 5

OWL 2 is an extension** and **revision of the 2004 version of OWL developed by the W3C Web Ontology Working Group.

Question 6

Write an enumeration of the days of the week with owl:oneOf

Answer 6

Question 7

Declare an instance of an #academicStaffMember in RDF

Answer 7

Question 8

True or false: OWL adopts the unique-names assumption of database systems

Answer 8

False

If two instances have a different name or ID does not imply that they are different individuals

Question 9

What RDF tag do you use to ensure different individuals are recognized as such?

Answer 9

owl:differentFrom

Question 10

What is the shorthand notation to assert pairwise inequality of all individuals in a list?

Answer 10

owl:allDifferent

Question 11

Property Separation

(Restriction of Features in OWL)

Answer 11

• The set of object properties and datatype properties are disjoint
• Therefore, the following can never be specified for data type properties:
  
  • ​owl:inverseOf
  • owl:FunctionalProperty
  • owl:InverseFunctiolnalProperty
  • owl:SymmetricProperty

Question 12

Which two assumptions does OWL inherit from Description Logic?

Answer 12

• The open-world assumption
• The non-unique-name assumption

Question 13

Open-World Assumption

Answer 13

• cannot conclude some statement x to be false simply because we cannot show x to be true
  
  • Question:“Did it rain in Tokyo yesterday?”
  • Answer:“I don’t know that it rained, but that’s not enough reason to conclude that it didn’t rain.”

Question 14

Closed-World Assumption

Answer 14

• allow deriving falsity from the inability to derive truth
  
  • Question:“Was there a big earthquake disaster in Tokyo yesterday?”
  • Answer:“I don’t know that there was, but if there had been such a disaster, I’d have heard about it. Therefore, I conclude that there wasn’t such a disaster.”

Question 15

By the use of two examples, one in databases and the other in web, describe how a database uses closed world and web uses open world assumptions.

Answer 15

Web present data about uncounted concepts, Consider the following statement: “Tim Smith with the ID of 785654549 is a citizen of France.” Now, what if you ask “Is Tim Smith with the ID of 785654549 a citizen of Malaysia?” Under a closed world assumption, the answer is “no” whereas under the open world assumption the answer is “not known”. Web is full of such kinds of data. Hence, open world assumption is used in a system with incomplete information, to which Web belongs.

On the other hand databases usually presents data about limited concepts, say a university. For instance, if the database of UOW shows that Tim Smith with the ID of 785654549 is not UOW’s student, definitely he is not UOW’s student.

Moreover in web non-unique names are used, and two different ID may show the same resource, whereas in database this not the case

Question 16

Future Extensions of OWL

Answer 16

• modules and imports
• defaults
• closed world assumption
• unique names assumption
• procedural attachments
• rules for property chaining

Question 17

Modules and Imports

Answer 17

• OWL only allows importing an entire ontology, not parts of it
• Modules in programming languages based on information hiding: state functionality, hide implementation details

Question 18

OWL builds upon ___ and ___ ___.

Answer 18

OWL builds upon RDF and RDF Schema.