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In information systems, a tag is a non-hierarchical keyword or term assigned to a piece of information (such as an Internet bookmark, digital image, or computer file). This kind of metadata helps describe an item and allows it to be found again by browsing or searching. Tags are generally chosen informally and personally by the item's creator or by its viewer, depending on the system. Tagging was popularized by websites associated with Web 2.0 and is an important feature of many Web 2.0 services. It is now also part of some desktop software. ==History== Labeling and tagging are carried out to perform functions such as aiding in classification, marking ownership, noting boundaries, and indicating online identity. They may take the form of words, images, or other identifying marks. An analogous example of tags in the physical world is museum object tagging. In the organization of information and objects, the use of textual keywords as part of identification and classification long predates computers. However, computer based searching made the use of keywords a rapid way of exploring records. Online and Internet databases and early websites deployed them as a way for publishers to help users find content. In 1997, the collaborative portal "A Description of the Equator and Some Other Lands" produced by documenta X, Germany, coined the folksonomic term ''Tag'' for its co-authors and guest authors on its Upload page. In "The Equator" the term ''Tag'' for user-input was described as an ''abstract literal or keyword'' to aid the user. Turned out in Web 1.0 days, all "Otherlands" users defined singular ''Tags'', and did not share ''Tags'' at that point. In 2003, the social bookmarking website Delicious provided a way for its users to add "tags" to their bookmarks (as a way to help find them later); Delicious also provided browseable aggregated views of the bookmarks of all users featuring a particular tag.〔(Screenshot of tags on del.icio.us ) in 2004 and (Screenshot of a tag page on del.icio.us ), also in 2004, both published by Joshua Schachter on July 9, 2007.〕 Flickr allowed its users to add their own text tags to each of their pictures, constructing flexible and easy metadata that made the pictures highly searchable.〔("An Interview with Flickr's Eric Costello" ) by Jesse James Garrett, published on August 4, 2005. Quote: "Tags were not in the initial version of Flickr. Stewart Butterfield...liked the way they worked on del.icio.us, the social bookmarking application. We added very simple tagging functionality, so you could tag your photos, and then look at all your photos with a particular tag, or any one person’s photos with a particular tag."〕 The success of Flickr and the influence of Delicious popularized the concept,〔An example is ("Folksonomies - Cooperative Classification and Communication Through Shared Metadata" ) by Adam Mathes, December 2004. It focuses on tagging in Delicious and Flickr.〕 and other social software websites – such as YouTube, Technorati, and Last.fm – also implemented tagging. Other traditional and web applications have incorporated the concept such as "Labels" in Gmail and the ability to add and edit tags in iTunes or Winamp. Tagging has gained wide popularity due to the growth of social networking, photography sharing and bookmarking sites. These sites allow users to create and manage labels (or “tags”) that categorize content using simple keywords. The use of keywords as part of an identification and classification system long predates computers. In the early days of the web keywords meta tags were used by web page designers to tell search engines what the web page was about. Today's tagging takes the meta keywords concept and re-uses it. The users add the tags. The tags are clearly visible, and are themselves links to other items that share that keyword tag. Knowledge tags are an extension of keyword tags. They were first used by Jumper 2.0, an open source Web 2.0 software platform released by Jumper Networks on 29 September 2008. Jumper 2.0 was the first collaborative search engine platform to use a method of expanded tagging for knowledge capture. Websites that include tags often display collections of tags as tag clouds. A user's tags are useful both to them and to the larger community of the website's users. Tags may be a "bottom-up" type of classification, compared to hierarchies, which are "top-down". In a traditional hierarchical system (taxonomy), the designer sets out a limited number of terms to use for classification, and there is one correct way to classify each item. In a tagging system, there are an unlimited number of ways to classify an item, and there is no "wrong" choice. Instead of belonging to one category, an item may have several different tags. Some researchers and applications have experimented with combining structured hierarchy and "flat" tagging to aid in information retrieval.〔(Tag Hierarchies ), research notes by Paul Heymann.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Tag (metadata)」の詳細全文を読む スポンサード リンク
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