Data that resides in a fixed field within a record or file is called structured data and have a defined schema. Unstructured data refers to information that either does not have a pre-defined data model and does not fit well into relational tables. Clustering gains importance in the fields of libraries (book ordering), insurance (identifying groups and identifying frauds), WWW (document classification and clustering weblog data). Available clustering algorithms work only with structured data and use medoids as parameter for clustering.