A little while ago I started a series about the structured web where I claimed that Meaning = Data + Structure. I followed up with a couple of posts on ways that structure can be added to user generated content, through user generated structure, and through inferring structure from domain knowledge. The third way that structure can be inferred is from user behavior, otherwise known as attention. As Wikipedia notes:
Attention economics is an approach to the management of information that treats human attention as a scarce commodity, and applies economic theory to solve various information management problems.
Alex Iskold has a good overview of the attention economy elsewhere at ReadWriteWeb.
By watching user behavior, by inferring intent and importance from the gestures and detritus of actions taken for other purposes, you can sometimes also infer structure about unstructured data. Google does this with its PageRank algorithm, Del.icio.us uses individual bookmarking to build a structured directory to the web, and Xobni maps social networks through analysis of your emailing patterns. Behavioral targeted advertising is based on the assumption that users display their interests through the websites they visit.
Using implicit data to infer structure requires making some assumptions about what each behavior means, but it can be a useful supplement to the other two methods of inferring data. As with inferring structure from domain knowledge, it requires a well defined ontology so that people and things can be mapped against it
Would love to hear more examples of using attention data to infer structure.