In this wiki page, I describe the types of things I would like the API to perform. Some of these are already available as Pentaho Servlets or JSP's, while other require more ingenuity. In the end, a front-end web developer should not need to write java or parse XML to interact with the Pentaho BI Platform.
The current plan is to implement the API in stages. First, I have created the components for interacting with Pentaho Metadata issuing MQL queries here. Next up is Action Sequence interaction and then I will leverage Roland's XMLA4JS for OLAP.