XML in Web data mining applications from broad terms can be divided into the following four categories: The first category, need for Web clients two or more heterogeneous applications to communicate between databases, as XML allows different sources of structured data very easily together. XML applied to customer needs with a variety of data sources to interact, the data may come from different databases, they have different complex formats. However, these databases between the client and only interact through a standard language that is XML. As the self-defining XML and scalability, it is sufficient to express all types of data. Customers can receive the data processing can also be passed between different databases.