Taxonomy, Ontology, Folksonomies, and SKOSA presentation by Janet Leu for LIS 882

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Taxonomy• The word “Taxonomy” is derived from two Greek stems : taxis

and nomos.

• Taxis – the arrangement or ordering of things• Nomos – anything assigned, usage or custom, law or ordinance.

• Taxonomy is a subject-based classification that arranges the terms in a controlled vocabulary , and allows related terms to be grouped together and categorized in ways that make it easier to find the correct term to use.

• Taxonomy is useful when searching for, or describing, an object. 2

A taxonomy is a kind of knowledge map.Chart taken from:

http://www.greenchameleon.com/gc/blog_detail/defining_taxonomy/

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Taxonomy = Knowledge Map• A good taxonomy means the user can immediately understand

the overall structure or knowledge domain covered by the taxonomy.

• A good taxonomy is also comprehensive, predictable, and easy to navigate. There is always a hierarchy and controlled vocabulary.

• The user will be able to accurately anticipate what types of resources they might find where.

• A taxonomy is semantic in the sense that it describes relationships between terms in the taxonomy.

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Another example of taxonomy• We start with a

generalized term, and keep getting more and more specific.• Almost anything may

be classified according to some taxonomic scheme, as long as there’s a logical hierarchy.

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Ontology• Ontology is the study of the categories of things that exist or may exist in

some domain. It’s the exact description of things and their relationships.

• An ontology is a formal specification of a shared conceptualization (as defined by Tom Gruber).

• In a philosophical sense, ontology is the study of entology and their relations. “What kinds of things can exist or can exist in the world, and what matter of relations can those things have to each other? Ontology is less concerned about what is than what is possible.” (as defined by Clay Shirky from semanticweb.org)

• Ontologies are considered one of the pillars of the Semantic Web. After an ontology is developed, it is used, reused, maintained, and related to other ontologies. Ontologies should be designed with these tasks in mind.

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Modularization of Ontologies• Upper, generic, top-level

ontology describes general knowledge, such as what is time and what is space.

• Domain ontology describes a domain, such as publishing or archives domain.

• Task ontology is ontology suitable for a particular task, such as creating a DC record in XML.

• Application ontology is developed for a specific application, such as assembling personal computers. 7

OWL – Web Ontology Language• OWL is a Semantic Web

Language (or, a Semantic Web Ontology) designed to represent rich, complex things, groups of things, and relationships between things.

• OWL is built on top of RDF• OWL is for processing

information on the web• OWL is written in XML• OWL is a WC3 standard

designed to be interpreted by computers, and not to be read by people. 8

An example of OWL with an RDF graph from (http://www.obitko.com/tutorials/ontologies-semantic-web/owl-example-with-rdf-graph.html

For example, Pizza OWL ontology expressed in RDF triples(subject, predicate, object):

@prefix :<http://example.com/pizzas.owl#> . @prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>.

@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .

@prefix owl: <http://www.w3.org/2002/07/owl#> .

:Pizza rdfs:subClassOf [ a owl:Restriction ; owl:onProperty :hasBase ; owl:someValuesFrom :PizzaBase ] ; owl:disjointWith :PizzaBase .

:NonVegetarianPizza owl:equivalentClass [ owl:intersectionOf ( [owl:complementOf

:VegetarianPizza] :Pizza ) ] . :isIngredientOf a owl:TransitiveProperty , owl:ObjectProperty ; owl:inverseOf :hasIngredient .

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Folksonomies• Folksonomies is a user-driven approach to organizing information.• Websites with folksonomies include two basic functions: users

can add “tags” to information and create navigational links out of those tags to help users find and organize that information later.

• Folksonomies address two disadvantages with taxonomies, in that the information within folksonomies is organized and maintained by users, so very little work has to be done by the designers after initially setting up the tagging system.

• Taxonomies can be time-consuming and expensive for design teams to implement. As a result, there may be broken taxonomies until the there is a complete redesign, and taxonomies may fail to reflect the language of users if they are not fully tested with the target population.

• Folksonomies improve usability and decrease support costs.10

Websites that use Folksonomies.

• Flickr•Del.icio.us•Wordpress• Tumblr•Blogspot•Blogger

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Folksonomies vs traditional classification

Folksonomies

• Doesn’t have structured hierarchical organization• Created by users• Utilizes a decentralized,

collaborative view• By definition, tagging

systems lack precision and currently do not provide synonym control.

Traditional classification

• Has structured hierarchical organization• Created by

organizational staff• Proposes an

authoritative centralized view• Has a high precision and

aims to avoid ambiguity12

Pros and cons of Folksonomies

PROS

• Great for serendipity and browsing

• Relational• Matches users’ real needs

and language• Stresses the learning

aspect• Tagging is cheaper than a

controlled vocabulary, and is better than nothing.

CONS

• Not aimed at a target approach or search

• Not hierarchical• Sometimes the language

isn’t precise enough• Doesn’t stress the location

aspect as much• Tagging is not as reliable as

a controlled vocabulary, or traditional schemes of classification. 13

SKOS (Simple Knowledge Organization Systems)

• A common data model for sharing and linking knowledge organization systems over the Web.

• Many knowledge organization systems, such as taxonomies and subject heading systems, share a similar structure and are used in similar applications.

• SKOS captures this similarity and makes it explicit, to enable data and technology sharing across diverse applications.

• SKOS also provides a standard, low-cost migration path for porting existing knowledge organization systems to the Semantic Web.

• May be used on its own, or in combination with formal knowledge representation languages, like OWL. 14

SKOS can be used to improve taxonomy.

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Sample label relationships in a pre-SKOS taxonomy, from http://www.ibm.com/developerworks/xml/library/x-skostaxonomy/

How SKOS can be used to improve taxonomy, part 2

16http://www.ibm.com/developerworks/xml/library/x-skostaxonomy/

SKOS and LCSH• The MARC21 Authority format distinguishes between authorized

(1XX) and non-authorized (4XX) headings.• SKOS vocabulary provides two properties: skos:prefLabel and

skos:altLabel.• These two labels allow a concept to be associated with both

preferred and alternate natural language labels.• The SKOS vocabulary allows both authorized and non-authorized

LCSH headings to be mapped directly to skos:prefLabel and skos:altLabel properties in a straightforward manner.

• Semantic relationships in LCSH/MARC easily translated into LCSH/SKOS.

• Links in LCSH/MARC use the established heading as references.• In LCSH/SKOS, conceptual resources are linked together by their

URIs.17

Garshol, Lars Marius. (October 26, 2004) Metadata? Thesauri? Taxonomies? Topic Maps! Retrieved fromhttp://www.ontopia.net/topicmaps/materials/tm-vs-thesauri.html

Gasser, Michael. (September 10, 2006). Word Senses and Taxonomies. Retrieved from http://www.indiana.edu/~hlw/Meaning/senses.html

Lambe, Patrick. (April 18, 2006). Defining Taxonomy. Retrieved from http://www.greenchameleon.com/gc/blog_detail/defining_taxonomy/

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Taxonomy Bibliography

Ontology Bibliography• Obitko, Marek. Modularization and Ontoligies. Retrieved

March 1, 2012, from http://www.obitko.com/tutorials/ontologies-semantic-web/modularization-of-ontologies.html

• Ontology. (n.d.). In Semantic Web Wiki. Retrieved March 1, 2012, from http://semanticweb.org/wiki/Ontology

• Smith, Michael K., Chris Welty and Deborah L. McGuiness. (February 10, 2004). OWL Web Ontology Language Guide. Retrieved from http://www.w3.org/TR/owl-guide/

• Sowa, John F. (November 29, 2010. Ontology. Retrieved from http://www.jfsowa.com/ontology/

• Welty, Chris. (April 2005). Semantic Web Ontologies. Retrieved from http://www.daml.org/meetings/2005/04/pi/Ontologies.pdf

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Folksonomies Bibliography• Mathes, Adam. (December 2004). Folksonomies – Cooperative

Classification and Communication Through Shared Metadata. Retrieved from http://www.adammathes.com/academic/computer-mediated-communication/folksonomies.html

• Porter, Joshua. (April 26, 2005). Folksonomies: A User-Driven Approach to Organizing Content. Retrieved from http://www.uie.com/articles/folksonomies/

• Quintarelli, Emanuele. (June 24, 2005). Folksonomies: Power to the People. Retrieved from http://www.iskoi.org/doc/folksonomies.htm

• Terdiman, Daniel. (February 1, 2005). Folksonomies Tap People Power. Retrieved from http://www.wired.com/science/discoveries/news/2005/02/66456?currentPage=all

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SKOS Bibliography• DuCharme, Bob. (May 10, 2011). Improve Your Taxonomy

Management Using the W3C SKOS Standard. Retrieved from http://www.ibm.com/developerworks/xml/library/x-skostaxonomy/

• Mikhalenko, Peter. (June 22, 2005). Introducing SKOS. Retrieved from http://www.xml.com/pub/a/2005/06/22/skos.html

• Miles, Alison, and Sean Bechhofer. (August 18. 2009). SKOS Simple Knowledge Organization System Reference. Retrieved from http://www.w3.org/TR/skos-reference/

• Summers, Ed., Antoine Isaac, Clay Redding, and Dan Krech. (2008). LCSH, SKOS and Linked Data. Retrieved from http://dcpapers.dublincore.org/ojs/pubs/article/viewFile/916/912

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