Open Collaboration Service client library
Attica is a Qt library that implements the Open Collaboration Services API version 1.6. The REST API is defined here: https://www.feedback.org/wiki/Specifications/open-collaboration-services
It grants easy access to services such as querying information about persons and contents. The library is used in KNewStuff3 as a content provider. In order to integrate with KDE's Plasma Desktop, a platform plugin exists in kdebase.
Your basic entry point for using Attica's functionality is the Attica::ProviderManager class.