MetaOCaml server pages: Web publishing as staged computation

Modern dynamic web services are really computer programs. Some parts of these programs run off-line, others run server-side on each request, and still others run within the browser. In other words, web publishing is staged computation, either for better performance, or because certain resources are available in one stage but not another. Unfortunately, the various web programming languages make it difficult to spread computation over more than one stage. This is a tremendous opportunity for multi-stage languages in general, and for MetaOCaml in particular.We present the design of MetaOCaml Server Pages. Unlike other languages in its genre, the embedded MetaOCaml code blocks may be annotated with staging information, so that the programmer may safely and precisely control which computation occurs in which stage. A prototype web server, written in OCaml, supports web sites with both static and dynamic content. We provide several sample programs and demonstrate the performance gains won using multi-stage programming.