The Web is a collection of multimedia documents in the form of HTML pages connected through hyperlinks. Unlike most search engines, which focus on information retrieval based on keywords, WebDB aims at supporting database-like comprehensive query functionalities as well navigation, and document generation functionalities with customizability. To support hypermedia database functionalities, we augment the traditional concepts of tables in relational databases and classes in object-oriented databases with notions of document formats and navigation. We design WQL (Web Query Language) as an HTML document manipulation language. WQL language statements contain two parts: SELECT. . . FROM. . . WHERE clauses for specifying retrieval of data contents from hypermedia databases and CREATE. . . AS. . . clauses for specifying the output HTML format and navigation of the query results. This paper presents the architecture of WebDB and its functionalities. The extension to SQL for hypermedia document manipulation, query, and navigation and implementation on NEC PERCIO OODBMS are described in detail.