Data-Intensive Web sites refer to the Web sites which integrate data from multiple heterogenous data sources. Building data-intensive Web sites is a data-management problem. Generally speaking, this process consists of three main programming tasks: accessing and integrating the data available in the site, building the structure of the site, i.e., specifying the data in each page and the links between pages, and generating the HTML representation of pages. In this paper, a Web page definition language named WPDL is proposed on XML techniques and related recommendations from W3C.A brief EBNF grammar rule of WPDL is given,and the key features of WPDL are described with wieh a couple of examples.It is argued that the three tasks can be separated with that kind of declarative query language.Thereby it is possible to maintain a data-intensive Web site with restructuring,reusability and integrityconstraint enforcement.