A Subjectivist Interpretation of Relevant Information

Abstract

One of the complaints frequently vented about current theories of information is that they are utterly hopeless when it comes to establish the actual relevance of some specific piece of information. Most of the times, most of us are interested in knowing not so much whether something is an instance of information, but rather how much that something is relevant for our purposes. Strictly speaking the complaint seems unfair. For no theory of information, from the purely syntactical to the most strongly semantic, is meant to cast any light on the phenomenon of relevance. Critics, however, have at least a sort of normative point. For they protest that such theories should care more about the relevance of what they model as information. If they do not, this is their problem and a reasonable explanation of why they can be largely disregarded when it comes to one's informative needs in real life. Starting from this general perspective, in this talk, I will a) introduce the general debate on informational relevancy in a variety of context, from search engines and information retrieval to online advertising, from juridical procedures to everyday information processes, from medial diagnosis to scientific experiments; b) argue that a general theory of relevant information may be provided by a counterfactual and metatheoretical analysis of the degree of relevance of (some information) i for an agent a as a function of the accuracy of i understood as an answer to a question q, given the probability that q might be asked by a. This analysis will uncover some intricate issues; and finally c) show that a subjectivist interpretation of relevance as indicated in (b) can satisfactorily account for all the main applications and interpretations of the concept of relevant information that may be encountered in contexts such as those listed in (a).