INTRODUCTION
In the age of information explosion, we all are overburdened with plethora of data and information. We know that information is power and data is the building block of information. If the data which we receive are arranged in logical and structured manner, then the power of information multiplies many times. But unfortunately over 90% of the data is available in unstructured format [1]. Searching the relevant pieces of information in unstructured data is very difficult. People find it problematic and very tough to extract information from very large number of data sources. In the age of competition every organisation wants to keep ahead from its competitor. Due to information explosion and change in nature of services and information demanded by the users, Information professional find it very challenging to satisfy the needs of the users. Now users want specific information within the plethora of available information, specific text within large volume of existing text. Now-a-days information professional are supposed to be the expert in information retrieval in terms of simple document retrieval to “knowledge” discovery. They need to make scrutiny and analysis of large quantity of data in different ways to get the desired result from the heap of data sets.