IR systems using the Boolean model have become less common in recent years, due in part to the popularity and increased ease of use of vector and probabilistic systems that accept keywords or natural language queries. Furthermore, front-end interfaces which allow Boolean or modified Boolean expressions, often called structured queries, have been implemented in both vector-based and probabilistic systems [45, ], in attempts to obviate the need for a strictly Boolean model.
While there is some Relevance Feedback literature regarding Boolean systems [33, , , ], they are mostly involved with adapting term selection formulas to append conjunctive terms to the expression and not generally germane to the purposes of this paper. Therefore, I will not address with the Boolean model further in this paper.