XML Databases store the bulk amount of XML data. Due to tremendous increase in the usage of XML in various applications, XML Documents must be made secured by storing them in a database. Querying XML is not nearly as mature as growing relational databases. The information stored in the XML database can be retrieved/added using XQuery. XQuery is a language that extracts the information from XML documents or databases. XQuery looks like similar to SQL.

XML Databases are categorized mainly into two types: An XML Enabled Database moves the data from XML documents to relational tables and vice-versa. Instead of modifying the XML documents every time the change occurs, it retrieves only that data which does not disturb the properties between tables and fields. This database checks whether the database schema is matching with the relational schema of the document before accessing the corresponding tables. Below is the architecture of XML Enabled Database in which XML-QL (XML Query Language) is applies as an add-on function to the RDBMS. The Relational QE (query engine) parses the XML-QL and converts it into SQL. The SQL is executed inside the RDBMS to perform operations with the Storage Manager. The Native XML database reserves the data of XML directly. Unlike Enabled database, the XML data will not undergo any conversion from XML format to SQL which increases the performance speed of the application. The storing and retrieval process of XML documents is done by XML Engine following the schemas defined. Below is the architecture of Native XML Database in which XML parser verifies the schema is correct or not and all the incoming data objects are well formed or not. The queries are performed using XQL.

• The information stored in the XML database can be retrieved/added using XQuery.
• XML Enabled Database moves the data from XML documents to relational tables with the help of SQL conversion.
• Native XML database reserves the data of XML directly.