This monograph presents a thesis work that attempts to utilize semantics to improve effectiveness in IR. The hypothesis is that with an improved representation of documents and by incorporating limited semantic knowledge, it is possible to improve the effectiveness of an information retrieval (IR) system. In this direction, statistical, hybrid and integrated IR models have been investigated. The conceptual graph (CG) based relevance feedback strategies and CG similarity measures proposed in this thesis are novel contributions. The techniques investigated in this work make use of ...