We argue that qualitative modeling provides a valuable way for students to learn. Learning to formulate, test, and revise models is a crucial aspect of understanding science and is critical to helping students become active, lifelong learners. Supporting students in articulating models of a domain and refining them through experience, reflection, and discussion with peers and teachers can lead to deeper, systematic understanding of science (for example, Reif and Larkin [1991]; Collins [1996]). However, modeling formalisms have traditionally been associated with creating mathematical models and deriving numeric results. Such approaches fail to capture many crucial aspects of models, such as the conditions under which a model is applicable, and are relatively inaccessible to younger children, such as middle school students.

We argue that qualitative modeling provides a valuable way for students to learn. Two modelbuilding environments, VMODEL and HOMER/- VISIGARP, are presented that support learners by constructing conceptual models of systems and their behavior using qualitative formalisms. Both environments use diagrammatic representations to facilitate knowledge articulation. Preliminary evaluations in educational settings provide support for the hypothesis that qualitative modeling tools can be valuable aids for learning.