“…The increasing number of distributed, autonomous and heterogeneous data sources, (ie: XML documents, relational database and HTML pages among others), has motivated the need for data integration systems, allowing users to query those sources transparently (Roth and Skritek., 2013;Pires et al, 2012). In this sense, dynamic data integration systems, as Peer Data Management Systems (PDMS) (Halevy et al, 2006), Grid (Zamboulis et al, 2010) or systems based on a pay-as-you-go strategy (Halevy et al, 2008), have been used to improve the data sharing of data sources distributed on the Web or on the cloud (Wall and Angryk, 2011). Some of these systems have a dynamic behaviour, i.e., their data sources have autonomy to join/leave the system and to change their own schemas.…”