Most database interfaces provide poor guidance on ad hoc query formulation, burdening users to learn, and to recall precisely the query language and the database. Kaleidoscope avoids this problem by guiding the user’s query construction actively. Based on a grammar specifying the syntax and semantics of an English-like Query Language (EnQL), the interface generates legitimate query constituents incrementally as menu choices. Additional intraquery guidance ensures the integrity of a partial query. The central theme of this paper is that to support Kaleidoscope’s style of usersystem interaction, the presence of a high-level data model is critical. The absence of an explicit model leads to ad hoc grammar design and query translation. Existing models are inadequate for supporting EnQL because of a significant conceptual gap between common English concepts and database representation of such concepts. This paper presents the features of Kaleidoscope, its data model for EnQL, and a mapp...