Special issue on soft computing applications to intelligent information retrieval on the Internet

This special issue encompasses eleven papers devoted to the recent developments in the applications of soft computing (SC) techniques to information retrieval (IR), both in the text and Web retrieval areas. The seed of the current issue were some of the presentations made in two special sessions organized by the guest editors in two different conferences: the First Spanish Conference on The scope of both special sessions was pretty related. In the former conference, the session topic was ''Applications of Evolutionary Computation to Information Retrieval'' while in the latter the session was entitled ''Artificial Intelligence Applications to Information Retrieval''. Five contributions were selected from these two special sessions in order to cover as much as possible the range of the different branches of SC in their application to IR. This way, these five works were instances of the four main SC constituent techniques: fuzzy logic, evolutionary computation, neural networks and probabilistic reasoning (Bayesian networks). The five original contributions were thoroughly revised and expanded to become the papers currently presented in this issue. On the other hand, with the aim of giving a wider outline of the current state of the topic, we decided to incorporate a group of papers written by recognized people in the field to the issue. Again, we tried to follow the idea of including a contribution on each of the SC techniques that had been applied to IR. This way, several representative researchers on the area were invited by the guest editors to write a paper on their specific expertise subject, thus resulting in four different areas: fuzzy logic, fuzzy clustering, Bayesian networks, and rough sets. Besides, Baeza-Yates was also invited by us to write an introductory paper exploring the existing challenges on Web retrieval and suggesting how SC can help to achieve them.