Today, a huge number of information sources are available via computer networks.
Thus, integration of heterogeneous information sources has been one of
the most important issues in recent advanced application environments.
We are developing an information integration system for structured document repositories, Web, and relational databases.
In this paper, we explain a graphical user interface (GUI) for the integration system.
Features of the GUI are as follows: (1) Interactive information exploration facilities which combine browsing and querying of both metadata and data.
(2) A visual query language to manipulate various complicated data structures in structured documents and Web such as nesting structures and hypertext linking structures.