"Tagging is changing how we find, use, and share information. And … it will have a long-term impact on our information landscapes," says author Gene Smith. (p. xii, emphasis in original) Although his book is written for people interested in designing and operating tagging systems, it can be usefully read as a general introduction to tagging.
In tagging systems, users mark, or tag, resources with descriptive words or phrases. In some systems, the users add and tag new resources; in others, they tag resources that are already there. The resources can be books, Web pages, photos, videos, or just about any kind of information. They can be files in the system or pointers to objects outside (links to Web sites or references to printed books, for example). The tags are the descriptive words or phrases added by users to describe the subjects of the resources or express an opinion ("funny"), and can be completely personal ("to read").
Tagging systems are designed and used for various purposes. Some are primarily for use in managing personal information for the user's own convenience, as, for example, Photo Gallery. Others allow people to collect interesting information and share it with others. Examples of these more social systems include Delicious for Web pages, Flickr for digital photos, SlideShare for PowerPoint presentations, and LibraryThing for personal book collections. In online stores like Amazon, tagging helps customers find items they want to purchase.
People tag to manage their personal information, to be able to find information when they need it. On the more social sites, they also tag to express themselves, to share interesting resources with others with or without actively engaging them, to explore interesting topics using resources tagged by others, to connect with others with shared interests, and to form groups around common interests. As a result, they collectively build up a knowledge base that benefits everyone and enhances the "findability" of its resources. The system benefits by capturing the user's knowledge and terminology and obtaining relatively inexpensive metadata that may stand alone or may be used to supplement more formal indexing structures. Tagging also identifies patterns in the use of resources, such as, for example, whether a particular resource enjoys lasting popularity, and why (is it useful, interesting, or funny?).
People may become users by, for example, signing up, being invited by existing members, joining the staff or membership of the organization operating the system (as in a business with an internal intranet or an association with a members-only Web site), or becoming customers of an online store. Users may connect with each other in various ways: passively observing, contacting others with similar interests, or forming groups to share resources around common interests.
Resources may be contributed by users, as in Flickr, Delicious, YouTube, and SlideShare, or may come from other sources, as in Amazon and other online stores. The system may limit resources to a single file type, like digital photos, or object type, such as books in personal collections. Resources and tags can, depending on the purpose of the system, be always private and visible only to the contributor, always public and visible to all users or to some users and not others, or public or private according to each contributor's choice.
As a purely private means of organizing information, tags are simple, flexible, and extensible. They can be tailored to the individual's interests and collection of items, and can be used alone or in combination with a more formal scheme. On the more social sites, where tags are also navigation aids for other users, some "tension points" appear between the personal and social aspects of tags.
- Are they primarily personal or primarily social?
- Can they be idiosyncratic or should they be standardized?
- How much, if at all, should the system influence or control users' choices by suggesting tags?
The balance struck between these aspects will be unique to each system. Soon after the appearance of the first tagging systems, information professionals began to notice that the accumulated tags were creating something like traditional controlled vocabularies without professional intervention as a purely serendipitous by-product. These vocabularies became known as folksonomies. As a result of the lack of control, tags are often "messy." Individual tags may have syntactic problems; the same tag may exist in variant forms (singular and plural, capitalized and lowercase, or different spellings); different tags may exist for the same concept (synonyms); and the overall tag set may have no discernable pattern.
Controlled vocabularies built by information professionals deal with these problems by standardizing the form and use of terms. Synonyms are identified and linked, and one is chosen as the preferred term. Taxonomies arrange terms in a hierarchical structure in which broad concepts are progressively subdivided into narrower topics, as in the Dewey decimal system, for instance. Many taxonomies and thesauri also identify and link related concepts in different branches of the hierarchy. However, controlled vocabularies of all types are expensive and time-consuming to produce, are difficult to update in a timely manner, and, while practical for defined collections, do not scale well, in particular, to the complete Web.
Folksonomies, on the other hand, have no formal structure other than their usage patterns, which can nevertheless reveal relationships among co-occurring terms. They are particularly useful for rapidly evolving fields or where nomenclature is fluid or uncertain.
There are ways to tame the "messiness" of tags. LibraryThing allows users to combine tags that appear to be synonyms and chooses the most used term as the preferred term. Other systems define top-level categories but not the complete hierarchical structure. Another strategy is to group tags into "facets" such as people, places, events, and resource types. Many systems suggest tags to users, drawn from tags previously used by the same user, popular tags used by others, tags for a particular type of resource, or a combination of all of these and other algorithms. Of course, tags and folksonomies can coexist beside and supplement more formal structures in the same system and can even be a source for new terms to be added after vetting to the formal structure.
The last chapters are more technical and explicitly aimed at system designers. Chapter 5, "Navigation and Visualization," discusses tag clouds and other navigational aids. A tag cloud is simply a grouping of tags in which the font size of each tag is proportional to how often the tag is used. Chapter 6, "Interfaces," discusses designing the text box for entering tags, methods of generating suggested tags, and managing and editing tags.
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