The aim of the SCHEMA Network of Excellence is to bring together a critical mass of universities, research centers, industrial partners and end users, in order to design a reference system for contentbased semantic scene analysis, interpretation and understanding. In this paper, recent advances in the development of the SCHEMA reference system are reported, focusing on the application of region-based image retrieval using automatic segmentation. More specifically, the first and the second version of the reference system are presented and the motivation behind the different approaches followed during the development of these two versions is discussed. Experimental results for both systems, using a common collection of images, are shown. Additionally, a comparative evaluation of the two versions both in terms of retrieval accuracy and in terms of time-efficiency is performed, allowing the evaluation of the system as a whole as well as the evaluation of the usability of different comp...