The Learning Engines (LE) model, developed at the University of Melbourne (Australia), supports the integration of rich learning activities into the World Wide Web. The model is concerned with the practical design, educational value, and reusability of software components. The model is focused on the academic teacher who is in the best position to conceive and apply novel learning objects (e.g., visualization, simulation, dialogue shell, interface) to meet particular discipline learning requirements. A key component of the model is the ability to engage the learner in tutorial-style dialogue. By incorporating other content resources and customized interface objects, the learning environment can be effectively extended. LE objects operate within an open, scalable technical framework that provides mechanisms for inter-object communication, database management, delivery, and authoring. This paper describes the LE model, including the Tutorial Itemset (a dialogue shell) and design issues, and the LE technical structure, including the communication framework, script, and Director core libraries. Future directions are also addressed. Three figures present: the Tutorial Itemset object displaying one of a set of question items; objects combined to create a tutorial dialogue centered around a simple visualization; and the Graphing Engine input device as focus of a tutorial dialogue. (Author/DLS)