Tag metadata

In online computer systems terminology, a tag is a non-hierarchical keyword or appellation assigned to a allotment of advice (such as an Internet bookmark, agenda image, or computer file). This affectionate of metadata helps call an account and allows it to be begin afresh by browsing or searching. Tags are about called artlessly and alone by the item's architect or by its viewer, depending on the system.

Tagging was affected by websites associated with Web 2.0 and is an important affection of abounding Web 2.0 services. It is now additionally allotment of some desktop software.

History and context

Labeling and tagging are agitated out to accomplish functions such as acceptable in classification, appearance ownership, acquainted boundaries, and advertence online identity. They may booty the anatomy of words, images, or added anecdotic marks. An akin archetype of tags in the concrete apple is building article tagging. In the organisation of advice and objects, the use of textual keywords as allotment of identification and allocation continued predates computers. However, computer based analytic fabricated the use of keywords a accelerated way of exploring records. Online and Internet databases and aboriginal websites deployed them as a way for publishers to advice users acquisition content. In 2003, the amusing bookmarking website Delicious provided a way for its users to add "tags" to their bookmarks (as a way to advice acquisition them later); Delicious additionally provided browseable aggregated angle of the bookmarks of all users featuring a accurate tag.[1] Flickr accustomed its users to add free-form tags to anniversary of their pictures, amalgam adjustable and accessible metadata that fabricated the pictures awful searchable.[2] The success of Flickr and the access of Delicious affected the concept,[3] and added amusingcomputer application websites – such as YouTube, Technorati, and Last.fm – additionally implemented tagging. "Labels" in Gmail are agnate to tags.

Websites that accommodate tags generally affectation collections of tags as tag clouds. A user's tags are advantageous both to them and to the beyond association of the website's users.

Tags may be a "bottom-up" blazon of classification, compared to hierarchies, which are "top-down". In a acceptable hierarchical arrangement (taxonomy), the artist sets out a bound cardinal of agreement to use for classification, and there is one actual way to allocate anniversary item. In a tagging system, there are an absolute cardinal of means to allocate an item, and there is no "wrong" choice. Instead of acceptance to one category, an account may accept several altered tags. Some advisers and applications accept experimented with accumulation structured bureaucracy and "flat" tagging to aid in advice retrieval

Examples

Within a blog

Many blog systems acquiesce authors to add free-form tags to a post, forth with (or instead of) agreement the column into categories. For example, a column may affectation that it has been tagged with baseball and tickets. Anniversary of those tags is usually a web articulation arch to an basis folio advertisement all of the posts associated with that tag. The blog may accept a aftereffect advertisement all the tags in use on that blog, with anniversary tag arch to an basis page. To reclassify a post, an columnist edits its account of tags. All access amid posts are automatically tracked and adapted by the blog software; there is no charge to backpack the folio aural a circuitous bureaucracy of categories.

For an event

An official tag is a keyword adopted by contest and conferences for participants to use in their web publications, such as blog entries, photos of the event, and presentation slides. Search engines can again basis them to accomplish accordant abstracts accompanying to the accident searchable in a compatible way. In this case, the tag is allotment of a controlled vocabulary.

Special types

Triple tags

See also: Microformat

A amateur tag or apparatus tag uses a appropriate syntax to ascertain added semantic advice about the tag, authoritative it easier or added allusive for estimation by a computer program. Amateur tags comprise three parts: a namespace, a predicate, and a value. For example, "geo:long=50.123456" is a tag for the bounded breadth alike whose amount is 50.123456. This amateur anatomy is agnate to the Resource Description Framework archetypal for information.

The amateur tag architecture was aboriginal devised for geolicious[5] in November 2004, to map Delicious bookmarks, and acquired added accepting afterwards its acceptance by Mappr and GeoBloggers[6] to map Flickr photos. In January 2007, Aaron Straup Cope at Flickr alien the appellation apparatus tag as an another name for the amateur tag, abacus some questions and answers on purpose, syntax, and use.[7]

Specialized metadata for bounded identification is accepted as geotagging; apparatus tags are additionally acclimated for added purposes, such as anecdotic photos taken at a specific accident or allotment breed application binomial nomenclature.[8]

Hashtags

Short letters on casework such as Twitter or identi.ca may be tagged by including one or added hashtags: words or phrases prefixed with the attribute #,[9][10] with assorted words concatenated, such as those in:

#Wikipedia is my admired affectionate of #encyclopedia

Then, a being can chase for the cord #Wikipedia and this tagged chat will arise in the chase agent results. These hashtags additionally appearance up in a cardinal of trending capacity websites, including Twitter's own advanced page. Such tags are case-insensitive, with CamelCase generally acclimated for readability.

Definitions for some hashtags are accessible at hashtag.org. Hashtags were invented on Twitter by Chris Messina.[11]

One abnormality specific to the Twitter ecosystem are micro-memes, which are appearing capacity for which a hashtag is created, acclimated broadly for a few days, again disappears.[12]

Other sites, such as Hashable, accept adopted the hashtag to use for added reasons.

The affection has been added to other, non-short-message-oriented services, such as the user animadversion systems on YouTube and Gawker Media; in the case of the latter, hashtags for blog comments and directly-submitted comments are acclimated to advance a added connected amount of user action alike back paid advisers are not logged into the website.[13][14] Real-time chase aggregators such as Google Real-Time Chase additionally abutment hashtags in amalgamated posts, acceptation that hashtags amid into Twitter posts can be hyperlinked to admission posts falling beneath that aforementioned hashtag; this has added enabled a appearance of the "river" of Twitter posts which can aftereffect from chase agreement or hashtags.

Advantages and disadvantages

In a archetypal tagging system, there is no absolute advice about the acceptation or semantics of anniversary tag, and a user can administer fresh tags to an account as calmly as applying earlier tags. Hierarchical allocation systems can be apathetic to change, and are abiding in the ability and era that created them.[15] The adaptability of tagging allows users to allocate their collections of items in the means that they acquisition useful, but the alone array of agreement can present challenges back analytic and browsing.

When users can advisedly accept tags (creating a folksonomy, as against to selecting agreement from a controlled vocabulary), the consistent metadata can accommodate homonyms (the aforementioned tags acclimated with altered meanings) and synonyms (multiple tags for the aforementioned concept), which may advance to inappropriate access amid items and inefficient searches for advice about a subject.[16] For example, the tag "orange" may accredit to the bake-apple or the color, and items accompanying to a adaptation of Apple's operating arrangement may be tagged "Mac OS X", "Lion", "software", or a array of added terms. Users can additionally accept tags that are altered inflections of words (such as atypical and plural),[17] which can accord to aeronautics difficulties if the arrangement does not accommodate stemming of tags back analytic or browsing. Larger-scale folksonomies abode some of the problems of tagging, in that users of tagging systems tend to apprehension the accepted use of "tag terms" aural these systems, and appropriately use absolute tags in adjustment to calmly anatomy access to accompanying items. In this way, folksonomies collectively advance a fractional set of tagging conventions.

Complex arrangement dynamics

Despite the credible abridgement of control, analysis has apparent that a simple anatomy of aggregate vocabularies emerges in amusing bookmarking systems. Collaborative tagging exhibits a anatomy of circuitous systems dynamics,[18] (or cocky acclimation dynamics). Thus, alike if no axial controlled cant constrains the accomplishments of alone users, the administration of tags that call altered assets (e.g., websites) converges over time to abiding ability law distributions.[18] Once such abiding distributions form, simple vocabularies can be extracted by analytical the correlations that anatomy amid altered tags. This breezy collaborative arrangement of tag conception and administration has been alleged a folksonomy.

Spamming

Tagging systems accessible to the accessible are additionally accessible to tag spam, in which bodies administer an boundless cardinal of tags or different tags to an account (such as a YouTube video) in adjustment to allure viewers. This corruption can be mitigated application animal or statistical identification of spam items.[19] The cardinal of tags accustomed may additionally be bound to abate spam.

Syntax

Some tagging systems accommodate a distinct argument box to access tags, so to be able to tokenize the string, a separator charge be used. Two accepted separators are the amplitude appearance and the comma. To accredit the use of separators in the tags, a arrangement may acquiesce for higher-level separators (such as citation marks) or escape characters. Systems can abstain the use of separators by acceptance alone one tag to be added to anniversary ascribe accoutrement at a time, although this makes abacus assorted tags added time-consuming.

A syntax for use aural HTML is to use the rel-tag microformat which uses the rel aspect with amount "tag" (i.e., rel="tag") to announce that the linked-to folio acts as a tag for the accepted context.