This chapter presents the data-intensive systems process engineering language (DISPEL) in enough detail for the reader to understand the aims and abilities of the language. DISPEL is a powerful programming language, while at the same time providing a high level of abstraction to ease the development of data-intensive applications. Much of the complexity and detail of a computation is embedded in the processing elements (PEs) themselves, which are created by specialists in their own domains. DISPEL functions and the registry provide further capabilities to abstract development for the user— for example, a function may encapsulate a complex composition of other constructs so that the resulting PE(s) can be directly used without knowledge of their underlying structure. The registry, empowered by the structural and domain type system, provides the ability to validate a DISPEL script in terms of more than simple syntax and provides a wealth of opportunities for optimization.