[Tagdb] tags and keywords - navigating folksonomies and text search

[Enis Soztutar]

> Currently how do people handle this in terms of implementation - do you 
> do a tag search first and then run a keyword search over those docs? The 
> other way around? What are the pro's and con's?
>
> If you are implementing tags in a relational database how does your tag 
> search interact with your keyword search?
> Practioners here's a chance to share your hard won wisdom and win 
> community glory in return ;-)
>   
Hi Nitin,

I know of some searching/tagging systems that works as a search engine, 
but displays the results with their tags. The tags, i believe, is due to 
delicious.

For the implementation part, it is obvious that db(for tagging) plus 
keyword search(inverted index) will not work efficiently. For example, 
you should query the db for every url, that you will display as a result 
for a keyword search, to find the mostly used tags of that url. A 
reasonable solution will be to use the inverted index instead of the db 
for tagging. Simpy (www.simpy.com) uses lucene for this purpose.

A search 2.0 engine can be built, by running the tagging system as 
usual, and indexing the urls with their common tags. I mean in the 
indexing phase of web crawling, tags of urls could be included in the 
main index as a separate field. These tags are then treated similar to 
anchor texts. Search query is extended to search the tags field also. A 
limitation for this approach is that, the indexing should be 
periodically updated, and the user information is not used. But if we 
know the querying user, then we can run the query in main index and the 
tag's index for the user, and then merge the results.