Exercise: familiarisation with ontologies

Ontologies

In information sciences an ontology is a specification of a conceptualisation.

This means they are a formal description of objects, concepts and entities that exist in a particular domain, along with the relationships among them 1. Ontologies are one of the essential pillars of the Semantic Web.

Datasets usually encode facts about individual objects and events, such as the following two facts about the Beatles (shown here in English rather than a database format):

The Beatles are a music group

The Beatles are a group

There is something odd about this pair of facts: having said that the Beatles are a music group, why must we add the more generic fact that they are a group?

Must we list these two facts for all music groups – not to mention all groups of acrobats or actors etc.? Must we also add all other consequences of being a music group, such as performing music and playing musical instruments?

Ontologies allow more efficient storage and use of data by encoding generic facts about classes (or types of object), such as the following:

Every music group is a group

Every theatre group is a group

It is now sufficient to state that the Beatles (and the Rolling Stones, etc.) are music groups, and the more general fact that they are groups can be derived through inference.

Ontologies thus enhance the value of data by allowing a computer application to infer, automatically, many essential facts that may be obvious to a person but not to a program.

A very related concept to an Ontology is the one of Vocabulary, at this level, the difference is too subtle to be useful to explain, think about both as synonyms for description of entities and relationships among them.

Exercise: describe yourself using FOAF vocabulary

The aim of this exercise is for you to familiarise yourself with ontologies used in the Web of data. We will start off by looking at the widely used FOAF vocabulary.

  1. Read the first three sections of ‘Introduction to FOAF’

  2. Explore the ‘FOAF cross-reference: Listing FOAF Classes and Properties’ defined by FOAF

Describe yourself using the FOAF vocabulary. What class are you? What properties do you have? Describe the place you work or study. Is it a group or an organization? What are its properties?

Share your response in the comments area. Have a look at other learners’ comments. If you can relate to a comment someone else has made, why not ‘Like’ it or leave a reply? You can filter comments by ‘Following’, ‘Most liked’ and ‘My comments’.


We will be looking at the web standards for the Semantic Web in greater detail later on this week.


This work is a derivative of ‘Using Linked Data Effectively’ by The Open University (2014) and licensed under CC by 4.0 International Licence adapted and used by the University of Southampton. http://www.euclid-project.eu/


References

  1. Gruber, T.R., 1993. A translation approach to portable ontology specifications. Knowledge acquisition, 5(2), pp.199-220. 

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Introduction to Linked Data and the Semantic Web

University of Southampton

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