Prototyping real-time vision systems: an experiment in DSL design

Describes the enhancement of XVision, a large library of C++ code for real-time vision processing, into FVision (pronounced "fission"), a fully-featured domain-specific language (DSL) embedded in Haskell. The resulting prototype system substantiates the claims of increased modularity, effective code reuse and rapid prototyping that characterize the DSL approach to systems design. It also illustrates the need for judicious interface design: relegating computationally expensive tasks to XVision (pre-existing C++ components) and leaving modular compositional tasks to FVision (Haskell). At the same time, our experience demonstrates how Haskell\´s advanced language features (specifically, parametric polymorphism, lazy evaluation, higher-order functions and automatic storage reclamation) permit a rapid DSL design that is itself highly modular and easily modified. Overall, the resulting hybrid system exceeded our expectations: visual tracking programs continue to spend most of their time executing low-level image processing code, while Haskell\´s advanced features allow us to quickly develop and test small prototype systems within a matter of a few days, and to develop realistic applications within a few weeks.