1 Faculty of Sciences and Technology, University of Coimbra, Pólo II Pinhal de Marrocos, 3030-290, Coimbra, Portugal. pha@dei.uc.pt.
2 Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, s/n, 4200-465, Porto, Portugal. dcs@fe.up.pt.
3 Institute of Business Information Systems, University of Applied Sciences Western Switzerland (HES-SO), Rue de la Jeunesse 1, 2800, Delémont, Switzerland. michael.schumacher@hevs.ch.
4 School of Engineering, University of Minho, Campus de Azurém, 4804-533, Guimarães, Portugal. lpreis@dsi.uminho.pt.
5 Oporto Polytechnic Institute, Rua Dr. Roberto Frias, 4200-465, Porto, Portugal. btf@estsp.ipp.pt.
6 Brazil IBM Research Lab, R. Tutóia, 1157, Vila Mariana, São Paulo, Brazil. marciaito@br.ibm.com.