Editorial: Selected papers from SBES '07

This Special Issue contains four extended papers selected from those presented in the 21st Brazilian Symposium in Software Engineering (SBES 2007) which took place in Joa?o Pessoa, state of Parai′ba, in the northeast of Brazil. This series of symposia, which is currently in its 23rd edition, is an initiative of the Software Engineering Special Committee (CEES) of the Brazilian Computing Society (SBC). The objective of SBES is to stimulate the exchange of experiences between research groups, disseminate the use of advanced software engineering techniques and tools and promote contact between participants and national and international invited speakers.