What does this exactly mean? I keep rereading the NY Times article but don't seem to grasp the concept.
I take it to mean that if I query on 'French revolution' any document written in the last few years might be equally suitable, and an older article with more links is likely to be the correct result for google to report. But if I query on 'football results' i am likely to be looking for a page produced or updated very recently. Hence QDF - the second of those queries requires freshness/newness in the search, but the first doesn't.
They try to do it now, but think they can improve. I guess it is quite 'brute force' at the moment. I guess a 'basic' implementation would look for words like 'news' in the query, which strongly suggest that QDF is needed, whereas a better implementation would look for more subtle indications. As an example, I was just looking for reviews of a particular bike, which has been in production for a few years but gets revamped / modified each year. The results of a search tend to bring up the older reviews of the now outdated models. I suppose that better QDF would understand that up to date reviews are more relevant than older ones, and put them higher in the results. Of course, I'm just speculating!
Actually, what it has to do with is the fact that on normal day to day queries, Google tends to give more weight to older more established pages. This leads sometimes to what webmasters will refer to as the Sandbox Effect. I think the theory is that spammers might have less of an attention span and always be after the quick buck, therefore it helps to defeat them by giving more weight to older sites. However, this can have an effect on new hot topics, things that might have had matching queries before, but that are not relevant to why people are searching on the phrase now. Therefore, they introduced a new factor named the QDF (Query Deserves Freshness). Basically it means that if the term falls under what could be classified as a hot topic, either because of a burst in searches for it, or an increase in the number of news stories or blog stories being written about it, or both, then they should lower the weight factor that they give on older domains/pages, so that the newer material being written about the subject now has a better chance of showing up higher in the serps. That whole bit about the French Revolution had nothing to do with QDF, btw... that was another problem altogether. -Michael