An ideal abstract model for parallel computation must carefully balance requirements for effective software engineering with requirements for efficient implementation. Models based on sets of fixed communication/computation patterns satisfy these requirements but, in general, the sets of patterns are chosen arbitrarily. Categorical data types are a way of building such models while automatically generating operations, equations, and a guarantee of completeness. We illustrate this construction, and its usefulness for practical problems, by building the type of chemical molecules and showing how molecular properties can be computed in parallel.