What is the difference between a thesaurus and a taxonomy?
A thesaurus usually includes more kinds of relationships for each term, than a simple taxonomy, namely associative relationships. A thesaurus is also more term focused, with an alphabetical arrangement of terms and their details, while a taxonomy is focused on the hierarchy.
Thesauri and taxonomies are both knowledge organization systems/controlled vocabularies that help information searchers find and retrieve the desired content. They both aim to support retrieval through improving precision and recall, and both allow the user to browse/navigate and explore for terms, based on their relationships with other terms. Both designations, "thesauri" and "taxonomies," are sometimes used interchangeably, and in some cases the distinctions are blurred, but usually there are differences.
It may be said that a thesaurus is like a taxonomy with the additional feature of associative relationships between terms, but the distinction is more complex than that. A thesaurus often has the immediate/direct purpose of serving consistent manual indexing, whereas a taxonomy supports end-user navigation/browsing. A Thesaurus focuses on terms and their relationships, whereas a taxonomy focuses on hierarchy and structure. What we call thesauri are expected to conform to standards, either ANSI/NISO Z 39.19 or ISO 2788 (to be replaced by ISO 25964), whereas taxonomies do not necessarily; they may comply only with the standard requirements for hierarchical relationships.
Thesauri are more commonly used for indexing/retrieving articles,reference documents, images and multimedia records. Taxonomies are more commonly used, for indexing/retrieving web pages, Intranet pages/content, and content management system pages/content. An individual term record display is also an option. Thesauri are usually displayed alphabetically, but often offer a hierarchical display option. Taxonomies are either hierarchical or faceted, but not alphabetical. Taxonomies do not have term record displays.
How do taxonomies relate to metadata?
Taxonomies can support metadata and thus are the source for terms in many descriptive metadata fields. Not all metadata uses taxonomies, and not all taxonomies are used for metadata support, though.
If a taxonomy is created solely for the purpose of hierarchical organization and navigation, such for folders on shared drives or libraries and folders in SharePoint, where users "put" a document in a folder, or as a part of a web site information architecture, then metadata may not be involved. Public web pages do have meta tags, and the position of a document in a hierarchical taxonomy could be a trigger to make that taxonomy term as a meta tag descriptor for the web page.
If, however, a taxonomy is used as a source of terms to index or tag documents, whereby these taxonomy terms are then attached to and associated with the document, then the taxonomy terms do become part of the metadata for the document (along with the document title, date, author, description, and other metadata). This is quite common. Cataloging systems, content management systems (including web content management systems for web sites and intranets), document management systems, records management systems, digital asset management system, etc. all support metadata for documents/digital assets.
Taxonomies or simply forms of controlled vocabularies can be used as source for terms in various separate metadata fields, such as: Topic/Subject, Location, Organization, Person Name, and Document Type. More specific, customized metadata fields may also be desired, such as Product Type, Brand Name, Regulation, Issuing Department, etc
How do taxonomies relate to ontologies?
Ontologies are more complex knowledge organization systems than taxonomies. In ontologies, terms are categorized by classes and customized semantic relationships exist between terms of different pairs of classes. Ontologies are also supported by different technology.
How does taxonomy relate to Google and to other search engines?
Web search engines, such as Google, don't use a true taxonomy, but rather term equivalency tables to help support common matches, such as misspellings. Enterprise search engines, on the other hand may incorporate a taxonomy for a more limited scope of content.
Is a taxonomy that supports search different than a taxonomy for browsing/navigation, or could it be the same one taxonomy?
It's better if they are different taxonomies. Although they may share many of the same terms, they are constructed differently for different purposes.
How is content tagged with a taxonomy?
It can be done manually, by human indexers, or automatically by an autocategorization or autoclassification system which is a component of some search software.
How does taxonomy relate to social media, like Twitter and Facebook?
Social networking, publishing and resource sharing sites such as Facebook, Twitter, Delicious and Flickr use a less formal kind of taxonomy dubbed a 'folksonomy' by Thomas Vander Wal. Users tag content with whatever word - real or self-generated - that they believe will describe the content and improve its findability. More...
How does taxonomy relate to my corporate Intranet?
Many enterprise search tools, portals and digital asset management systems use taxonomies to better organize content and improve the chances it is found when needed. A taxonomy customized for your organization can increase efficiency, reduce duplication of content and reduce costs associated with recreating and storing redundant content.