Schema Creation in Programming

The creation of plan schemes is examined in a naturalistic, longitudinal study of problem solving. Ten novice programmers each wrote eight Pascal programs to solve a series of problems. Their protocols were analyzed to determine how declarative programming knowledge was used to create simple procedural program plans, and how the simple plans were used to create complex plans. Plan creation showed a process of backward development, from the goal to the plan focus, that port of the plan that directly implements the goal. Once defined; it is expanded to create the complete plan, showing backward development of plan parts from the focus. Once the plan is complete, it may be stored as a plan schema and retrieved in subsequent problem solving. The plan will then show forward development as it is implemented in schema order, the order in which plan pieces occur in the finished program. The change from backward development during creation to forward development after retrieval was strongly evident in the statistical analysis of the protocol data. Previous studies of novice programming, which showed only forward development, ore explained as special cases of this more general model, cases in which schema knowledge was available to the problem solver.