Wrapper in data mining is a program that extracts content of a particular information source and translates it into a relational form. Many web pages present structured data – telephone directories, product catalogs, etc. formatted for human browsing using HTML language. Structured data are typically descriptions of objects retrieved from underlying databases and displayed in Web pages following some fixed templates. Software systems using such resources must translate HTML content into a relational form. Wrappers are commonly used as such translators. Formally, a wrapper is a function from a page to the set of tuples it contains.