Tag (metadata)

Source: Wikipedia, the free encyclopedia.
A tag cloud with terms related to Web 2.0

In

Internet bookmark, multimedia, database record, or computer file). This kind of metadata helps describe an item and allows it to be found again by browsing or searching.[1] Tags are generally chosen informally and personally by the item's creator or by its viewer, depending on the system, although they may also be chosen from a controlled vocabulary.[2]
: 68 

Tagging was popularized by

Overview

People use tags to aid

classification, mark ownership, note boundaries, and indicate online identity. Tags may take the form of words, images, or other identifying marks. An analogous example of tags in the physical world is museum object tagging. People were using textual keywords to classify information and objects long before computers. Computer based search algorithms
made the use of such keywords a rapid way of exploring records.

Tagging gained popularity due to the growth of

social networking websites.[2] These sites allow users to create and manage labels (or "tags") that categorize content using simple keywords. Websites that include tags often display collections of tags as tag clouds,[a] as do some desktop applications.[b]
On websites that aggregate the tags of all users, an individual user's tags can be useful both to them and to the larger community of the website's users.

Tagging systems have sometimes been classified into two kinds: top-down and bottom-up.

taxonomies are created by an authorized group of designers (sometimes in the form of a controlled vocabulary), whereas bottom-up taxonomies (called folksonomies) are created by all users.[3]: 142  This definition of "top down" and "bottom up" should not be confused with the distinction between a single hierarchical tree structure (in which there is one correct way to classify each item) versus multiple non-hierarchical sets (in which there are multiple ways to classify an item); the structure of both top-down and bottom-up taxonomies may be either hierarchical, non-hierarchical, or a combination of both.[3]: 142–143  Some researchers and applications have experimented with combining hierarchical and non-hierarchical tagging to aid in information retrieval.[7][8][9] Others are combining top-down and bottom-up tagging,[10] including in some large library catalogs (OPACs) such as WorldCat.[11][12]: 74 [13][14]

When tags or other taxonomies have further properties (or

relationships and attributes, they constitute an ontology.[3]
: 56–62 

Metadata tags as described in this article should not be confused with the use of the word "tag" in some software to refer to an automatically generated cross-reference; examples of the latter are tags tables in Emacs[15] and smart tags in Microsoft Office.[16]

History

The use of keywords as part of an identification and classification system long predates computers. Paper data storage devices, notably edge-notched cards, that permitted classification and sorting by multiple criteria were already in use prior to the twentieth century, and faceted classification has been used by libraries since the 1930s.

In the late 1970s and early 1980s, the

function call and that function's definition.[17] This use of the word "tag" did not refer to metadata tags, but was an early use of the word "tag" in software to refer to a word index
.

web search engines what the web page was about, but these keywords were only visible in a web page's source code
and were not modifiable by users.

"A Description of the Equator and Some ØtherLands", collaborative hypercinema portal, produced by documenta X, 1997. User upload page associating user contributed media with the term Tag.

In 1997, the collaborative portal "A Description of the Equator and Some ØtherLands" produced by documenta X, Germany, used the folksonomic term Tag for its co-authors and guest authors on its Upload page.[18] In "The Equator" the term Tag for user-input was described as an abstract literal or keyword to aid the user. However, users defined singular Tags, and did not share Tags at that point.

In 2003, the

Atom web syndication standard provided a "category" element for inserting subject categories into web feeds, and in 2007 Tim Bray proposed a "tag" URN.[23]

Examples

Within a blog

Many systems (and other web

web link
leading to an index page listing all of the posts associated with that tag. The blog may have a sidebar listing all the tags in use on that blog, with each tag leading to an index page. To reclassify a post, an author edits its list of tags. All connections between posts are automatically tracked and updated by the blog software; there is no need to relocate the page within a complex hierarchy of categories.

Within application software

Some

desktop applications and web applications feature their own tagging systems, such as email tagging in Gmail and Mozilla Thunderbird,[12]: 73  bookmark tagging in Firefox,[24] audio tagging in iTunes or Winamp, and photo tagging in various applications.[25] Some of these applications display collections of tags as tag clouds.[b]

Assigned to computer files

There are various systems for applying tags to the files in a computer's file system.

In

Mac OS X.[28]

Several semantic file systems that implement tags are available for the Linux kernel, including Tagsistant.[29]

Microsoft Windows allows users to set tags only on Microsoft Office documents and some kinds of picture files.[30]

ISO standard for embedding metadata into popular image, video and document file formats, such as JPEG and PDF, without breaking their readability by applications that do not support XMP.[31] XMP largely supersedes the earlier IPTC Information Interchange Model. Exif is a standard that specifies the image and audio file formats used by digital cameras, including some metadata tags.[32] TagSpaces is an open-source cross-platform application for tagging files; it inserts tags into the filename.[33]

For an event

An official tag is a keyword adopted by events and conferences for participants to use in their web publications, such as blog entries, photos of the event, and presentation slides.[34] Search engines can then index them to make relevant materials related to the event searchable in a uniform way. In this case, the tag is part of a controlled vocabulary.

In research

A researcher may work with a large collection of items (e.g. press quotes, a bibliography, images) in digital form. If he/she wishes to associate each with a small number of themes (e.g. to chapters of a book, or to sub-themes of the overall subject), then a group of tags for these themes can be attached to each of the items in the larger collection.[35] In this way, freeform classification allows the author to manage what would otherwise be unwieldy amounts of information.[36]

Special types

Triple tags

A triple tag or machine tag uses a special

semantic information about the tag, making it easier or more meaningful for interpretation by a computer program.[37] Triple tags comprise three parts: a namespace, a predicate, and a value. For example, geo:long=50.123456 is a tag for the geographical longitude coordinate whose value is 50.123456. This triple structure is similar to the Resource Description Framework
model for information.

The triple tag format was first devised for geolicious in November 2004,[38] to map Delicious bookmarks, and gained wider acceptance after its adoption by Mappr and GeoBloggers to map Flickr photos.[39] In January 2007, Aaron Straup Cope at Flickr introduced the term machine tag as an alternative name for the triple tag, adding some questions and answers on purpose, syntax, and use.[40]

Specialized metadata for geographical identification is known as geotagging; machine tags are also used for other purposes, such as identifying photos taken at a specific event or naming species using binomial nomenclature.[41]

Hashtags

A hashtag is a kind of metadata tag marked by the prefix #, sometimes known as a "hash" symbol. This form of tagging is used on

VK and Instagram
. The hash is used to distinguish tag text, as distinct, from other text in the post.

Knowledge tags

A knowledge tag is a type of

hyperlinks, or references that are collected in tag profiles (a kind of ontology).[42] These tag profiles reference an information resource that resides in a distributed, and often heterogeneous, storage repository.[42]

Knowledge tags are part of a

Enterprise 2.0 methodologies for users to capture insights, expertise, attributes, dependencies, or relationships associated with a data resource.[3]: 251 [43] Different kinds of knowledge can be captured in knowledge tags, including factual knowledge (that found in books and data), conceptual knowledge (found in perspectives and concepts), expectational knowledge (needed to make judgments and hypothesis), and methodological knowledge (derived from reasoning and strategies).[43] These forms of knowledge often exist outside the data itself and are derived from personal experience, insight, or expertise. Knowledge tags are considered an expansion of the information itself that adds additional value, context, and meaning to the information. Knowledge tags are valuable for preserving organizational intelligence that is often lost due to turnover, for sharing knowledge stored in the minds of individuals that is typically isolated and unharnessed by the organization, and for connecting knowledge that is often lost or disconnected from an information resource.[44]

Advantages and disadvantages

In a typical tagging system, there is no explicit information about the meaning or semantics of each tag, and a user can apply new tags to an item as easily as applying older tags.[2] Hierarchical classification systems can be slow to change, and are rooted in the culture and era that created them; in contrast, the flexibility of tagging allows users to classify their collections of items in the ways that they find useful, but the personalized variety of terms can present challenges when searching and browsing.

When users can freely choose tags (creating a folksonomy, as opposed to selecting terms from a controlled vocabulary), the resulting metadata can include homonyms (the same tags used with different meanings) and synonyms (multiple tags for the same concept), which may lead to inappropriate connections between items and inefficient searches for information about a subject.[45] For example, the tag "orange" may refer to the fruit or the color, and items related to a version of the Linux kernel may be tagged "Linux", "kernel", "Penguin", "software", or a variety of other terms. Users can also choose tags that are different inflections of words (such as singular and plural),[46] which can contribute to navigation difficulties if the system does not include stemming of tags when searching or browsing. Larger-scale folksonomies address some of the problems of tagging, in that users of tagging systems tend to notice the current use of "tag terms" within these systems, and thus use existing tags in order to easily form connections to related items. In this way, folksonomies may collectively develop a partial set of tagging conventions.

Complex system dynamics

Despite the apparent lack of control, research has shown that a simple form of shared vocabulary emerges in social bookmarking systems. Collaborative tagging exhibits a form of complex systems dynamics (or self-organizing dynamics).[47] Thus, even if no central controlled vocabulary constrains the actions of individual users, the distribution of tags converges over time to stable power law distributions.[47] Once such stable distributions form, simple folksonomic vocabularies can be extracted by examining the correlations that form between different tags. In addition, research has suggested that it is easier for machine learning algorithms to learn tag semantics when users tag "verbosely"—when they annotate resources with a wealth of freely associated, descriptive keywords.[48]

Spamming

Tagging systems open to the public are also open to tag spam, in which people apply an excessive number of tags or unrelated tags to an item (such as a YouTube video) in order to attract viewers. This abuse can be mitigated using human or statistical identification of spam items.[49] The number of tags allowed may also be limited to reduce spam.

Syntax

Some tagging systems provide a single

tokenize the string, a separator must be used. Two popular separators are the space character and the comma. To enable the use of separators in the tags, a system may allow for higher-level separators (such as quotation marks) or escape characters. Systems can avoid the use of separators by allowing only one tag to be added to each input widget
at a time, although this makes adding multiple tags more time-consuming.

A syntax for use within

rel attribute with value "tag" (i.e., rel="tag") to indicate that the linked-to page acts as a tag for the current context.[50]

See also

Notes

  1. ^
    Blogger and WordPress
    can display tag clouds.
  2. ^
    Windows application that permits tagging files and displaying a tag cloud.[6]

References

  1. .
  2. ^ .
  3. ^ .
  4. ^ .
  5. ^ Hampton-Smith, Sam (12 April 2013). "The pro designer's guide to photo organization". creativebloq.com. Archived from the original on 16 April 2013. Retrieved 10 March 2017. As with all the other options here, meta data can be added to individual files to help improve their find-ability, and uniquely the tag cloud field within Leap's interface allows you to quickly drill down to individually labelled files without fuss.
  6. PC Magazine. Archived from the original
    on 11 July 2015. Retrieved 10 March 2017.
  7. ^ Heymann, Paul; Garcia-Molina, Hector (2006). Collaborative creation of communal hierarchical taxonomies in social tagging systems (Technical report). Stanford University. Summarized in: Heymann, Paul (2006). "Tag hierarchies". infolab.stanford.edu. Archived from the original on 25 June 2016. Retrieved 10 March 2017.
  8. S2CID 56905311
    .
  9. .
  10. .
  11. ^ Wilson, Katie (2007). "OPAC 2.0: next generation online library catalogues ride the Web 2.0 wave!". Online Currents. 21 (10): 406–413. Archived from the original on 2017-07-31. Retrieved 2017-03-11.
  12. ^
    OCLC 148910044
    .
  13. ^ Willey, Eric (2011). "A cautious partnership: the growing acceptance of folksonomy as a complement to indexing digital images and catalogs". Library Student Journal. Retrieved 10 March 2017.
  14. S2CID 62681953
    .
  15. . Calling a function defined in one compilation unit from within another is analogous to cross references in large hypertext documents. By using tags tables, the Emacs environment enables the user to turn program source code into powerful hypertext documents.
  16. . You can turn on smart tags for a field to make it easier to cross-reference data between the Access database and Microsoft Outlook (or another personal information and e-mail program) and the Web.
  17. . EMACS is an M.I.T. display editor designed to be 'extensible, customizable, and self-documenting' [...] Another interesting facility for program editing is the TAGS package. The separate program TAGS builds a TAGS table containing the file name and position in that file in which each application program function is defined. This table is loaded into EMACS; specifying the command Meta, function name causes EMACS to select the appropriate file and go to the proper function definition within that file.
  18. ^ "A Description of the Equator and Some ØtherLands". aporee.org. Archived from the original on 18 August 2001. Retrieved 10 March 2017.
  19. ^ See, for example: 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.
  20. ^ Garrett, Jesse James (4 August 2005). "An Interview with Flickr's Eric Costello". Archived from the original on 18 October 2017. Retrieved 21 September 2017. Tags were not in the initial version of Flickr. Stewart Butterfield wanted to add them. He 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. Soon thereafter, users started telling us that what was really interesting about tagging was not just how you've tagged your photos, but how the whole Flickr community has been tagging photos. So we started seeing a lot of requests from users to be able to see a global view of the tagscape.
  21. ^ Mathes, Adam (December 2004). "Folksonomies: cooperative classification and communication through shared metadata". adammathes.com. Archived from the original on 9 March 2017. Retrieved 10 March 2017.
  22. OCLC 709712928
    .
  23. ^ Bray, Tim (1 February 2007). "A Uniform Resource Name (URN) namespace for tag metadata". tbray.org. Archived from the original on 5 November 2016. Retrieved 10 March 2017.
  24. ^ "Firefox tip: find bookmarks faster with tags". blog.mozilla.org. Mozilla Foundation. Archived from the original on 12 October 2016. Retrieved 10 March 2017.
  25. OCLC 606841528
    .
  26. .
  27. ^ Siracusa, John (22 October 2013). "OS X 10.9 Mavericks: The Ars Technica Review: Tags". arstechnica.com. Ars Technica. Archived from the original on 9 January 2017. Retrieved 10 March 2013.
  28. ^ Cherp, Aleh (17 March 2011). "Tagging". macademic.org. Academic workflows on a Mac. Archived from the original on 30 April 2016. Retrieved 10 March 2017.
  29. ^ "Extended attributes and tag file systems". lesbonscomptes.com. 2 July 2015. Archived from the original on 11 August 2016. Retrieved 10 March 2017.
  30. ^ Schultz, Greg (23 March 2011). "Tag your files for easier searches in Windows 7". techrepublic.com. TechRepublic. Archived from the original on 29 August 2016. Retrieved 10 March 2017.
  31. ^ Gasiorowski-Denis, Elizabeth (22 March 2012). "Adobe Extensible Metadata Platform (XMP) becomes an ISO standard". iso.org. International Organization for Standardization. Archived from the original on 10 March 2017. Retrieved 10 March 2017.
  32. OCLC 969844731
    .
  33. ^ Devcic, Ivana Isadora (9 October 2015). "Tag, you're it! How to manage files on Linux with TagSpaces". makeuseof.com. MakeUseOf. Archived from the original on 28 December 2016. Retrieved 10 March 2017.
  34. ^ Finch, Curt (26 May 2011). "Hashtag techniques for businesses". inc.com. Inc. Magazine. Retrieved 10 March 2017.
  35. ^ Parry, David (11 March 2007). "Tagging files—or how to keep research organized". academhack.outsidethetext.com. Archived from the original on 2 August 2016. Retrieved 10 March 2017.
  36. S2CID 31128922
    .
  37. .
  38. ^ Maron, Mikel (5 November 2004). "geo.lici.us: geotagging hosted services". brainoff.com. Archived from the original on 28 April 2007. Retrieved 10 March 2017.
  39. ^ Catt, Dan (11 January 2006). "Advanced Tagging and TripleTags". Archived from the original on 11 October 2007. Retrieved 10 March 2017.
  40. ^ Straup Cope, Aaron (24 January 2007). "Machine tags". flickr.com. Archived from the original on 20 April 2016. Retrieved 10 March 2017.
  41. ^ "The Encyclopedia of Life Flickr group rules". flickr.com. Encyclopedia of Life. Archived from the original on 10 February 2017. Retrieved 10 March 2017. Includes the required use of a taxonomy machine tag.
  42. ^
    OCLC 798568503
    .
  43. ^ .
  44. ^ Alavi, Maryam; Leidner, Dorothy E. (February 1999). "Knowledge management systems: issues, challenges, and benefits". Communications of the AIS. 1 (2es): 1.
  45. S2CID 1946917
    .
  46. ^ Devens, Keith (24 December 2004). "Singular vs. plural tags in a tag-based categorization system (such as del.icio.us)". keithdevens.com. Archived from the original on 10 May 2012. Retrieved 10 March 2017.
  47. ^
    S2CID 13935265
    .
  48. .
  49. ^ Heymann, Paul. "Tag spam". stanford.edu. Stanford University. Retrieved 10 March 2017.
  50. ^ "Microformats wiki: rel='tag'". microformats.org. 10 January 2005. Retrieved 10 March 2017.