A folksonomy is a system of classification derived from the practice and method of collaboratively creating and managing tags to annotate and categorize content; this practice is also known as collaborative tagging, social classification, social indexing, and social tagging. Folksonomy, a term coined by Thomas Vander Wal, is a portmanteau of folk and taxonomy. Vander Wal explains some of the characteristics of folksonomies by identifying two types: broad and narrow. A broad folksonomy is one in which multiple users tag particular content with a variety of terms from a variety of vocabularies, thus creating a greater amount of metadata for that content. A narrow folksonomy, on the other hand, occurs when a few users, primarily the content creator, tag an object with a limited number of terms. While both broad and narrow folksonomies enable the searchability of content by adding textual description - or access points - to an object, a narrow folksonomy does not have the same benefits as a broad folksonomy, which allows for the tracking of emerging trends in tag usage and developing vocabularies.  Folksonomies became popular on the Web around 2004 as part of social software applications such as social bookmarking and photograph annotation. Tagging, which is one of the defining characteristics of Web 2.0 services, allows users to collectively classify and find information. Some websites include tag clouds as a way to visualize tags in a folksonomy. A good example of a social website that utilizes folksonomy is 43 Things. However, tag clouds visualize only the vocabulary but not the structure of folksonomies, as do tag graphs.
An empirical analysis of the complex dynamics of tagging systems, published in 2007, has shown that consensus around stable distributions and shared vocabularies does emerge, even in the absence of a central controlled vocabulary. For content to be searchable, it should be categorized and grouped. While this was believed to require commonly agreed on sets of content describing tags (much like keywords of a journal article), recent research has found that, in large folksonomies, common structures also emerge on the level of categorizations. Accordingly, it is possible to devise mathematical models of collaborative tagging that allow for translating from personal tag vocabularies (personomies) to the vocabulary shared by most users.
The term folksonomy is generally attributed to Thomas Vander Wal. It is a portmanteau of the words folk (or folks) and taxonomy that specifically refers to subject indexing systems created within Internet communities. Folksonomy has little to do with taxonomy — the latter refers to an ontological, hierarchical way of categorizing, while folksonomy establishes categories (each tag is a category) that are theoretically "equal" to each other (i.e., there is no hierarchy, or parent-child relation between different tags).
Folksonomy is unrelated to folk taxonomy, a cultural practice that has been widely documented in anthropological and folkloristic work. Folk taxonomies are culturally supplied, intergenerationally transmitted, and relatively stable classification systems that people in a given culture use to make sense of the entire world around them (not just the Internet).
Semantic Web 
Folksonomy may hold the key to developing a Semantic Web, in which every Web page contains machine-readable metadata that describes its content. Such metadata would dramatically improve the precision (the percentage of relevant documents) in search engine retrieval lists. However, it is difficult to see how the large and varied community of Web page authors could be persuaded to add metadata to their pages in a consistent, reliable way; web authors who wish to do so experience high entry costs because metadata systems are time-consuming to learn and use. For this reason, few Web authors make use of the simple Dublin Core metadata standard, even though the use of Dublin Core meta-tags could increase their pages' prominence in search engine retrieval lists. In contrast to more formalized, top-down classifications using controlled vocabularies, folksonomy is a distributed classification system with low entry costs. The Insemtives project is investigating methods of motivating users to contribute semantic content.
Library Catalogs 
Some libraries are adding tagging features into their online public access catalog, or OPACs, in addition to use of standardized subject headings, in order to encourage a more social, participatory, or Web 2.0 nature to the catalog. While this empowers users to contribute to an otherwise closed cataloging system, it can only supplement and not completely replace traditional cataloging.
The study of the structuring or classification of folksonomy is termed folksontology. This branch of ontology deals with the intersection between highly structured taxonomies or hierarchies and loosely structured folksonomy, asking what best features can be taken by both for a system of classification. The strength of flat-tagging schemes is their ability to relate one item to others like it. Folksonomy allows large disparate groups of users to collaboratively label massive, dynamic information systems. The strength of taxonomies are their browsability: users can easily start from more generalized knowledge and target their queries towards more specific and detailed knowledge. Folksonomy looks to categorize tags and thus create browsable spaces of information that are easy to maintain and expand.
See also 
- Peters, Isabella (2009). "Folksonomies. Indexing and Retrieval in Web 2.0.". Berlin: De Gruyter Saur.
- Pink, Daniel H. (December 11, 2005). "Folksonomy". New York Times. Retrieved 14 July 2009.
- Lambiotte, R, and M Ausloos. 2005. Collaborative tagging as a tripartite network. http://arxiv.org/abs/cs.DS/0512090.
- Vander Wal, Thomas. "Explaining and Showing Broad and Narrow Folksonomies". Retrieved 2013-03-05.
- Vander Wal, Thomas. "Folksonomy Coinage and Definition". Retrieved 2009-07-06.
- Lamere, Paul (June 2008). "Social Tagging And Music Information Retrieval". Journal of New Music Research 37 (2): 101–114. doi:10.1080/09298210802479284.
- Lohmann, S., Diáz, P.: Representing and Visualizing Folksonomies as Graphs - A Reference Model, Proc. International International Working Conference on Advanced Visual Interfaces, ACM Press, 2012.
- Harry Halpin, Valentin Robu, Hana Shepherd The Complex Dynamics of Collaborative Tagging, Proc. International Conference on World Wide Web, ACM Press, 2007.
- V. Robu, H. Halpin, H. Shepherd Emergence of consensus and shared vocabularies in collaborative tagging systems, ACM Transactions on the Web (TWEB), Vol. 3(4), art. 14, 2009.
- Robert Wetzker, Carsten Zimmermann, Christian Bauckhage, and Sahin Albayrak I tag, you tag: translating tags for advanced user models, Proc. International Conference on Web Search and Data Mining, ACM Press, 2010.
- Vanderwal, T. (2005). "Off the Top: Folksonomy Entries." Visited November 5, 2005. See also: Smith, Gene. "Atomiq: Folksonomy: social classification." Aug 3, 2004. Retrieved January 1, 2007.
- http://vanderwal.net/folksonomy.html Origin of the term
- M. Koivunen, Annotea and Semantic Web Supported Annotation.
- Berlin, B. (1992). Ethnobiological Classification. Princeton: Princeton University Press.
- Fields, Kenneth (2007) "Ontologies, categories, folksonomies: an organised language of sound." Cambridge.
- Mohamed, Khaled A.F. (2006) "The impact of metadata in web resources discovering"
- Marchiori, Massimo (1998) "The limits of Web metadata, and beyond"
- Jin Zhang and Alexandra Dimitroff (2004). "JIS: Internet search engines' response to metadata Dublin Core implementation"
- Corey A. Harper and Barbara B. Tillett, Library of Congress controlled vocabularies and their application to the Semantic Web
- Steele, T. (2009). The new cooperative cataloging. Library Hi Tech, 27 (1), 68-77
- McFadden, S., Venker Weldenbenner, J. (2009). Collaborative Tagging: Traditional Cataloging Meets the “Wisdom of Crowds”. The Serials Librarian 58 (1-4), 55-60.
- Van Damme, Céline; et al. "FolksOntology: An Integrated Approach for Turning Folksonomies into Ontologies". Retrieved April 20, 2012.
- Trattner, C., Körner, C., Helic, D.: Enhancing the Navigability of Social Tagging Systems with Tag Taxonomies. In Proceedings of the 11th International Conference on Knowledge Management and Knowledge Technologies, ACM, New York, NY, USA, 2011
Additional references 
- "Folksonomy", The New York Times, 2005-12-11
- "Folksonomies Tap People Power", Wired News, 2005-02-01
- "Folksonomy and science communication". Information Services & Use (27): 97–103. 2007. – Folksonomies as a tool for professional scientific databases
- SocialTagging.org provides short definitions of key terms related to tagging and folksonomies
- Vanderwal's definition of folksonomy
- Vanderwal's take on Wikipedia's definition of folksonomy