Two Operators to Define and Manipulate Themes of a Document Collection

In this paper, we propose the theme model, which will provide the end user with join and meet operators to define and manipulate themes. These operators have properties that cannot be reduced to the classical logic operators, thus allowing the researchers to model the informative content of documents in a novel way and to rank documents in ways other than those provided by the classical logic. To this end, we introduce the main definitions and properties of the theme model and we link the model to a number of related techniques, thus suggesting how the model can be implemented and applied.