Complex sentence: He was Editor-in-Chief of the ACM Transactions on Database Systems from 2001 to 2007 and has served previously as Associate Editor of the International Journal on Very Large Databases and the IEEE Transactions on Knowledge and Data Engineering.
Split into simpler sentences: He was Editor-in-Chief of the ACM Transactions on Database Systems from 2001 to 2007. Additionally, he has served as an Associate Editor of the International Journal on Very Large Databases and the IEEE Transactions on Knowledge and Data Engineering.