Taxonomy of tagging systems

This is my cheat sheet for the paper "Position Paper, Tagging, Taxonomy, Flickr, Article, ToRead" (PDF). I'd recommend reading it (if you find tagging interesting you probably already have) but I wanted to extract its two conceptual taxonomies. They're helpful for thinking about tagging systems but the paper buries them a bit.

The paper deals mainly with social tagging systems, and it uses the classic tripartite model of tagging: resource (the thing being tagged), user (the person doing the tagging) and tags (the tag connecting the two).

System Design and Attributes

"We describe some key dimensions of tagging systems’ design that may have immediate and considerable effect on the content and usefulness of tags generated by the system. For each dimension in our taxonomy, we note the ways in which the location of a system on this dimension may impact the behavior of the system. Some of these dimensions listed below interact; a decision along one of them may determine, or at least be correlated with, the system’s placement in another."

1. Tagging Rights - who can tag what?
   1. Self-tagging - users can only tag their own contributions (e.g. Technorati)
   2. Permission-based - users decide who can tag their resources (e.g. Flickr), or some other design on the continuum between self-tagging and free-for-all
   3. Free-for-all - any user can tag any resource
2. Tagging Support - how does the interface support tag entry?
   1. Blind tagging - user cannot see the other tags assigned to the resource they're tagging
   2. Viewable tagging - users can see the other tags assigned to the resource they're tagging
   3. Suggestive tagging - user sees suggested tags for the resource they're tagging
3. Aggregation - how are tags aggregated for a given resource?
   1. Bag-model - the same tag can be assigned to a resource multiple times (allowing statistics to be generated and users to see if there is agreement among taggers about the content of the resource). This is very del.icio.us.
   2. Set-model - a tag can be applied only once to a resource, like in Flickr.
4. Type of Object - what kind of resource is being tagged?
   1. "any object that can be virtually represented can be tagged or used in a tagging system"
5. Source of Material - how does the resource get there?
   1. Supplied by participant - user contributes the resource
   2. Supplied by system - like in the ESP Game
6. Resource Connectivity - how are resources connected to each other in the system?
   1. Linked - resources are linked (with hyperlinks or other links)
   2. Grouped - resources can be assigned to groups (like Flickr groups)
   3. None
7. Social Connectivity - how are users connected to each other in the system?
   1. Linked - users are connected as contacts, friends or other social links
   2. Grouped - users can join groups
   3. None

User Incentives

"The motivations to tag can be categorized into two high-level practices: organizational and social. The first arises from the use of tagging as an alternative to structured filing; users motivated by this task may attempt to develop a personal standard and use common tags created by others. The latter expresses the communicative nature of tagging, wherein users attempt to express themselves, their opinions, and specific qualities of the resources through the tags they choose."

1. Future Retrieval - marking something so it can found later (aka refindability)
2. Contribution and sharing - adding tags for the "value of known or unkown audiences"
3. Attract Attention - "to get people to look one's own resources"
4. Play and Competition - formally in the ESP Game, informally in tags like squaredcircle (over 40,000 photos!) and sometaithurts
5. Self Presentation - "to write a user’s own identity into the system as a way of leaving their mark on a particular resource"
6. Opinion Expression - making value judgements, e.g. bullshit

The paper compares Del.icio.us and Flickr and finds significant differences:

In nearly every category within our system taxonomy, Flickr occupies an alternative space from Del.icio.us: it contains user-contributed resources as opposed to global; tagging rights are restricted to self-tagging (and at best permission-based, although in practice self-tagging in most prevalent) instead of a free-for-all; tags are aggregated in sets instead of bags; and finally, the interface mostly affords for blind-tagging instead of suggested-tagging.

I'll have to revisit broad v. narrow folksonomies, but it seems like the main difference is in the aggregation. (Bags are broad, sets are narrow.)

I think there's set of system owner incentives that influence the system design. Those could include:

• facilitate collaboration and knowledge sharing among users
• obtain descriptive metadata about resources (e.g. ESP Game and Google Image Labeler)
• enhance resource findability
• increase system use through participation (e.g. the BBC regional message boards)
• identify patterns in resource usage (e.g. obtaining value judgements that identify the quality of the resource)
• generate revenue
• augment existing metadata/classification efforts

These aren't mutually exclusive or exhaustive, and some of them correlate with user incentives (e.g. enhance findability matches with the user incentive future retrieval).