One of the interesting things about tagging and tags is that it can change over time and is context sensitive. Something that might be tagged generically as politics one week could be tagged with scandal the next. The idea of of a time-based tag map for items has been discussed elsewhere and I believe there are at least a couple demo’s out in the wild.

Another service that is coming about is tag/keyword suggestions including text analysis. There are multiple services available including TagYu and Yahoo’s Term Extraction service. While some may argue that having suggestions changes what people tag, one of the interesting side affects is to see common themes among documents. An example just popped up that used TagYu to recommend tags for recent State of the Union addresses. Common themes appear to be ‘poverty’ and ‘socialjustice’.

I expect more and more things related to keywords and term extraction to come about as it can help in giving relevant links to other information or just finding information that is relevant in the first place. When doing research it may be helpful to have documents linked by theme or keywords instead of just whatever document type they are. I can foresee this being easier with government documents where it may be easier to get the full text for analysis.