Document clustering using graph based document representation with constraints

Document clustering is an unsupervised approach in which a large collection of documents (corpus) is subdivided into smaller, meaningful, identifiable, and verifiable sub-groups (clusters). Meaningful representation of documents and implicitly identifying the patterns, on which this separation is performed, is the challenging part of document clustering. We have proposed a document clustering technique using graph based document representation with constraints. A graph data structure can easily capture the non-linear relationships of nodes, document contains various feature terms that can be non-linearly connected hence a graph can easily represents this information. Constrains, are explicit conditions for document clustering where background knowledge is use to set the direction for Linking or Not-Linking a set of documents for a target clusters, thus guiding the clustering process. We deemed clustering is an ill-define problem, there can be many clustering results. Background knowledge can be used to drive the clustering algorithm in the right direction. We have proposed three different types of constraints, Instance level, corpus level and cluster level constraints. A new algorithm Constrained HAC is also proposed which will incorporate Instance level constraints as prior knowledge; it will guide the clustering process leading to better results. Extensive set of experiments have been performed on both synthetic and standard document clustering datasets, results are compared on standard clustering measures like: purity, entropy and F-measure. Results clearly establish that our proposed approach leads to improvement in cluster quality.