Web 2.0: Implementing tags?

Question

The trend in Web 2.0 sites is to support user generated (assigned) tags (Amazon, Flickr). Is there a recommended approach (algorithm) or a software application or a best practice document to quickly implement a tagging solution that is scalable (performance-wise)?
Thanks.

Answer 1

My recommendation is to use a SQL table:

tblTag
int objectID - primary key
varchar(30) tag - primary key
int weight

This way, tags are stored as few times as necessary - if a person tags and the tag already exists for the given object, then increment its weight - otherwise append the tag. This should take care of performance (additional performance gains by caching the tag groupings by object).

The tagging score cutoff is going to be different for every site. It really depends on how many tags you want to display, and how you want to display them. In a tag cloud, you can simply set a minimum cutoff or use more sophisticated ranking logic to balance between number of tags and weight. (i.e. start with the most weighted object and keep listing until you hit the maximum number of tags or the minimum weight)

Answer 2

complicated aspect. do a search over bing and yahoo. just that can help!