- Program co-chair of the Second International Workshop on Collaborative Social Network (CollaborateSN'10) in conjunction with IEEE CollaborateCom'10,Chicago, Illinois, USA, October 9-12, 2010.
- Program chair for the 15th ACM Symposium on Access Control Models and Technologies (SACMAT) (SACMAT 2010) Pittsburg, USA, 9-11, 2010.
- Workshop co-chair for the 6th International Conference on Collaborative Computing: Networking, Applications and Worksharing (CollaborateCom'10) Chicago, Illinois, USA, October 9-12, 2010.
- Program co-chair of the First International Workshop on Collaborative Social Network (CollaborateSN'09) in conjunction with IEEE CollaborateCom'09,Crystal City,Washington D.C., USA, November 11-14, 2009.
- Program co-chair of the First International Workshop on Secure Service Computing (SSC'09) in conjunction with IEEE APSCC 2009, Singapore, December 7-11, 2009.
- Tutorial co-chair for the 5th International Conference on Collaborative Computing: Networking, Applications and Worksharing (CollaborateCom'09) Crystal City, Washington D.C., USA, November 11-14, 2009.
- General chair for the 14th ACM symposium on access control models and technologies (SACMAT) (SACMAT 09) Stresa, Italy, June 3-5, 2009.
- Tutorial co-chair for the 4th International Conference on Collaborative Computing: Networking, Applications and Worksharing (CollaborateCom'08) Orlando, FL, USA, November 13-16, 2008.
- Program co-chair for the first International Workshop on Secure Semantic Web (SSW'08) in conjunction with the 24th International Conference on Data Engineering (ICDE'08),Cancun, Mexico, April 7-12, 2008.
- In the organizing Committee of the ACM Symposium on Access Control Models and Technologies (SACMAT 2003), Como, Italy.