ZOO API
ZOO API is a Javascript library designed to make the WPS Process creation and chaining easier.
It works server-side using the Mozilla foundation JavaScript engine, SpiderMonkey.
It is based on server-side adaptations of OpenLayers and Proj4js adaptation for handling formats and projections. It allows to easily convert vector formats (GML, KML, GeoJSON, etc).
The ZOO API let you orchestrate WPS services simply and offers the ability to add logic and controls in the WPS chaining.
Read the ZOO API documentation
Check the ZOO API source code