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About Thing 9

Purpose: An ontology is a system for organizing and describing entities and their relationships, using properties, attributes, and controlled vocabularies. 

Learning Outcomes: Understand what ontologies are and how they enable the reuse of data.

Intended Audience: Intermediate

Author: Lizzy Baus, Macalester College

Expected Duration: 45-60 minutes

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This work is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported License.

Getting Started

When you’re working with large amounts of data (including metadata), you need some way to organize the information. A good way to do this is to make use of an ontology. An ontology is a system of classes, properties, attributes, etc. that work together to define and describe different entities unambiguously. 

Many people who work with library catalogs will be familiar with the idea of a controlled vocabulary: a set list of terms that can fill a particular slot in a record, with no variations. For instance, Library of Congress Subject Headings are one such controlled vocabulary. For each concept, there is exactly one way it appears in the list. 

This is the main principle behind the idea of an ontology: an ontology defines what the available slots are and what things can go in those slots. They are very useful for helping machines understand relationships and meaning in a set of metadata. They also enable information to be encoded in very predictable ways, which allows for greater possibilities when it comes to manipulating and reusing data (a major goal of Linked Data!). One of the most salient ontologies for the library world is the BIBFRAME ontology. This is the model that has been developed for describing library resources without relying on the current MARC standard (which is not very Linked Data-friendly). 





Explore the BIBFRAME Ontology.

  • Take a look at the lengthy lists of classes and properties (feel free to skim!). 
    Click on a few items that catch your eye, and read the info box about each one. Notice that these contain links between classes and properties that are related to one another. 
  • You may find that some classes have much more extensive info boxes. Compare, for instance, the box for "Illustration" with that for "Instance."
  • What does the amount of information suggest about each class or property and how it might be used in describing a resource? 

Explore the vocabularies described on the Linked Open Vocabularies website.

  • Choose two different vocabularies, for example dcterms
  • Look at the graphs showing links into and out of the vocabulary. Notice how many other ontologies link to your chosen one, and how many your vocabulary links out to. Think about what this might mean for the interoperability of this vocabulary. 
  • Click on the link to the homepage for your ontology. What kind of information is provided there? What audience does this seem to be written for? Is there information missing?
  • Think about what kind of information is best suited to using this ontology. 


What is an example of an ontology you use in your daily life? How does it work with your data? What kinds of information are difficult to capture in a formal ontology? Consider sharing your thoughts in the Comments section at the bottom of the page.

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What is an example of an ontology you use in your daily life? How does it work with your data? What kinds of information are difficult to capture in a formal ontology?