Bag-of-Terms IR Ranking Model Performance Bound Analysis

Most traditional retrieval models are based on bag-of-term representations, and they model the relevance based on various collection statistics. Despite these efforts, it seems that the performance of bag-of-term based retrieval functions has reached plateau, and it becomes increasingly difficult to further improve the retrieval performance. Thus, one important research question is whether we can provide any theoretical justifications on the empirical performance bound of basic retrieval functions.