Questionnaires are an important medium for collecting information in diverse areas of society (scientific surveys, tax filing, auditing guidance, etc.). We are interested in a domain-specific language (DSL) to automatically generate questionnaire software from declarative specifications. This note describes an important aspect of the semantics of such a DSL: what goes on when users fill out a form? The formalism is based on the epistemic notion of information update and has a wide range of applications. It provides a formal interpretation for query forms, and for the process of answering such forms. The attractiveness of the approach is in the fact that asking questions, providing partial answers to questions, and providing full answers to questions, are all modeled by the same mechanism of constraining a range of possibilities.