Yahoo BOSS, Now With Key Terms

I’d just hit “publish” on my last post about the challenges of faceted search for the web when I saw this post from Jeff about Yahoo announced an extension to their public BOSS API that provides “key terms” for search results.

Jeff quotes this excerpt from their description:

Key Terms is derived from a Yahoo! Search capability we refer to internally as “Prisma.”… Key Terms is an ordered terminological representation of what a document is about. The ordering of terms is based on each term’s frequency and its positional and contextual heuristics…Each result contains up to 20 terms describing the document.

Yes, I know, key terms aren’t a faceted classification. And I don’t know what quality or consistency this feature provides. Still, it’s a step towards addressing the first and most serious challenge raised in the Microsoft researchers’ position paper. And it’s nice to see news about Yahoo beyond the saturation coverage of Jerry Yang stepping down.

By Daniel Tunkelang

High-Class Consultant.

9 replies on “Yahoo BOSS, Now With Key Terms”

Cool! A step in the right direction indeed, but a small one. It would be great if they also reported the term frequency for each term, and perhaps allowed a follow-on query to get IDF scores or other components that go into a ranking for each term. That way, a smart client could have some insight into how to use these terms for its own purposes.


I had the impression that the Google search API was rather limited. I certainly haven’t seen search applications built on top of the Google API that compare to those built on top of Yahoo BOSS, e.g., Duck Duck Go (

Perhaps someone here has tried both and can offer a more informed comparison?


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