The CitySDK Mobility API, developed by Waag Society is a layer-based data distribution and service kit. Part of CitySDK, a European project in which eight cities (Manchester, Rome, Lamia, Amsterdam, Helsinki, Barcelona, Lisbon and Istanbul) and more than 20 organisations collaborate, the CitySDK Mobility API enables easy development and distribution of digital services across different cities.
Although the initial focus in developing this part of the API was on mobility, the approach chosen allows any (open) data to be made available in a uniform and flexible manner.
A running implementation of the api can be found at http://dev.citysdk.waag.org; this is also where you'll find additional documentation.