We now take a slight detour from search to look at classification and clustering.
Classification and clustering have many things in common with document retrieval.
In fact, many of the techniques that proved to be useful for ranking documents
can also be used for these tasks.Classification and clustering algorithms
are heavily used in most modern search engines, and thus it is important to have
a basic understanding of how these techniques work and how they can be applied
to real-world problems.We focus here on providing general background knowledge
and a broad overview of these tasks.