Swets's theory of information retrieval allows the 'systems' and 'language', a recognition that retrieval threads of document weighting formulae, probabilistic performance can be tailored to suit individual needs in a measures of effectiveness, and management theory to be systematic way, and confirmation that question woven into a coherent pattern. Benefits of the theory Generality is a pivotal feature of the retrieval process. are the beginnings of a quantitative description of The hypotheses involved are still in need of rigorous retrieval languages, a clear distinction between retrieval experimental testing.