1. No category

Taxonomy, Ontology,
Folksonomies, and
SKOS
A 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.
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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.
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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.
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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.
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Websites that use Folksonomies.
• Flickr
• Del.icio.us
• Wordpress
• Tumblr
• Blogspot
• Blogger
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Folksonomies vs traditional classification
Folksonomies
Traditional classification
• 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.
• Has structured
hierarchical organization
• Created by
organizational staff
• Proposes an
authoritative centralized
view
• Has a high precision and
aims to avoid ambiguity
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Pros and cons of Folksonomies
PROS
CONS
• 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.
• 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.
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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.
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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
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http://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.
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Taxonomy Bibliography
Garshol, Lars Marius. (October 26, 2004) Metadata? Thesauri?
Taxonomies? Topic Maps! Retrieved from
http://www.ontopia.net/topicmaps/materials/tm-vsthesauri.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_taxo
nomy/
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Ontology Bibliography
• Obitko, Marek. Modularization and Ontoligies. Retrieved
March 1, 2012, from
http://www.obitko.com/tutorials/ontologies-semanticweb/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/computermediated-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?c
urrentPage=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/xskostaxonomy/
• 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/
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