The ambitious goal set out for TREC 2009 was to have a collection of 1 billion web pages. One dataset that can be shared by several tracks (specifically, the Entity, Million query, Relevance feedback, and Web tracks).
In November 2008, when this was discussed at the TREC 2008 conference, people were concerned with two main questions: (1) Is it possible to create such crawl (given the serious time constraints)? (2) Are we going to be able to handle (at least, index) this amount of data?
Jamie Callan was confident that they (the Language Technologies Institute at Carnegie Mellon University) could build this crawl by March 2009. His confidence was not unfounded, since they had managed to create a crawl of a few hundreds of millions of web pages earlier. Yet, the counter for the one billion documents collection was to be started from 0 again…
Against this background, let us fast forward to the present. The crawl has recently completed and the dataset, referred to as ClueWeb09, is now available. It is 25 terabytes uncompressed (5 terabytes compressed), which brings me back to the troubling question: are we going to be able to handle that? We (being ILPS) will certainly do our best to step up to the challenge. I shall post about our attempts in detail later on.
But, it is a fact that doing retrieval on 1 billion documents is too big of a bite for many research groups, as it calls for nontrivial software and hardware architecture (note that it is 40 times more data than the Gov2 corpus, which I believe was the largest web crawl available to the research community so far with its 25 million documents). Therefore, a “Category B” subset of the collection is also available, consisting of “only” 50 million English pages. Some of the tracks (the Entity track for sure) will use only the Category B subset in 2009.