In 1994, he spent six months at the Institute for Logic Language and Computation (ILLC), University of Amsterdam, visiting prof. J. van Benthem. The visit was supported by a grant from the Italian Consiglio Nazionale delle Ricerche (CNR). Since then, he visited ILLC several times for shorter periods.
He is member of the Association for Computing Machinery (ACM), the Association for Logic Programming (ALP), and the European Association for Theoretical Computer Science (EATCS).