5th International Symposium on Rules (RuleML) co-located with the 22nd International Join Conference on Artificial Intelligence (IJCAI), Barcelona, Spain, July 2011. Rule-Based Policies, Reputation and Trust Co-Chair. [ http ]

12th IEEE International Policies for Distributed Systems and Networks (POLICY 2011), Pisa, Italy, June 2011. Program Co-Chair.

8th Extended Semantic Web Conference (ESWC'11), Crete, Greece, June 2011. In-Use Track Chair.

User Profile Data on the Social Semantic Web (UWEB), Heraklion, Greece, May 2011. Co-Organizer and Program Committee.

2nd Workshop on Trust and Privacy on the Social and Semantic Web (SPOT'10), Heraklion, Greece, May 2010. Co-Organizer and Program Committee.

1st Workshop on Trust and Privacy on the Social and Semantic Web (SPOT'09), Heraklion, Greece, June 2009. Co-Organizer and Program Committee.

7th International Semantic Web Conference, Karlsruhe, Germany, October 2008. Workshop Chair. [ http ]

IEEE International Policies for Distributed Systems and Networks (POLICY 2008), Palisades, NY, USA, June 2008. IEEE Computer Society. System Demonstrations Chair.

1st International Workshop on Privacy Enforcement and Accountability with Semantics (PEAS) in conjunction with the 6th International Semantic Web Conference, Busan, Korea, November 2007. Co-Organizer and Program Committee. [ http ]

Special Issue of Computers and Human Behavior Journal on Electronic Games and Personalized eLearning Processes. Elsevier, 2007. Editorial Board.

Special Issue of Simulation & Gaming Journal on eGames and Adaptive eLearning. A practical approach, 2007. Editorial Board.

2nd Semantic Web Policy Workshop (SWPW) in conjunction with the 5th International Semantic Web Conference, Athens, Georgia, USA, November 2006. Co-Organizer and Program Committee. [ http ]

Joint International Workshop on Professional Learning, Competence Development and Knowledge Management, Heraklion, Greece, October 2006. Co-Organizer.

Models of Trust for the Web Workshop (MTW) in conjunction with the 15th International World Wide Web Conference, Edinburgh, UK, May 2006. Co-Organizer and Program Committee. [ .html ]

Daniel Olmedilla, Nobuo Saito, and Bernd Simon, editors. Special Issue (April 2006) of the Journal of Educational Technology and Society (endorsed by IEEE Technical Committee on Learning Technology) on Interoperability of Educational Systems, volume 9, April 2006. Guest Editor.

Daniel Olmedilla, Nobuo Saito, and Bernd Simon, editors. Proceedings of the WWW'05 Workshop on Interoperability of WebBased Educational Systems in conjunction with the 14th International World Wide Web Conference, Chiba, Japan, May 2005. Co-Organizer. [ .html ]

Jennifer Golbeck, Piero A. Bonatti, Wolfgang Nejdl, Daniel Olmedilla, and Marianne Winslett, editors. Proceedings of the ISWC'04 Workshop on Trust, Security, and Reputation on the Semantic Web in conjunction with the 3rd International Semantic Web Conference, volume 127 of CEUR Workshop Proceedings, Hiroshima, Japan, November 2004. Technical University of Aachen (RWTH). Co-Organizer and Program Committee. [ http ]

Applying Machine Learning to Ads Integrity at Facebook. Keynote at the 8th International ACM Web Science Conference 2016, May 2016.

Applying Machine Learning to Ads Integrity at Facebook. Keynote at Big Data Technology Summit 2016, February 2016. [ http ]

How to build a data science team. Invited talk at SecurITy 2014, October 2014.

Big data & data science @ XING. Invited talk at IIR Technology Praxisforum Big Data & Data Science 2013, November 2013. [ .pdf ]

Big data & data science @ XING. Invited talk at Big Data Success Stories 2013, November 2013.

Data science @ XING. Invited talk at Digital Consumer Business Workshop 2013, September 2013.

Invited talk at big data & data science @ XING. Big Data Minds 2013, September 2013.

Invited talk at big data & data science: What is the problem to solve? use case driven technology selection, architecture and solution design. Bitkom Big Data Summit 2013, June 2013. [ http ]

Invited talk at data science and analysis @ XING. Big Data Management 2013, April 2013. [ .pdf ]

[1] Journal of Web Semantics. Elsevier, 2011. Reviewer. [ http ]

IEEE Communications Letters. IEEE, 2011. Reviewer. [ http ]

IEEE Transactions on Industrial Informatics. IEEE, 2009. Reviewer. [ http ]

Journal of Educational Technology and Society (endorsed by IEEE Technical Committee on Learning Technology), 2008. Executive Peer-Reviewer. [ http ]

Journal of Web Semantics. Elsevier, 2009. Reviewer. [ www: ]

Information Sciences. Elsevier, 2009. Reviewer. [ www: ]

Journal of Educational Technology and Society (endorsed by IEEE Technical Committee on Learning Technology), 2008. Executive Peer-Reviewer. [ http ]

World Wide Web Journal. Springer, 2008. Reviewer. [ http ]

IEEE Transactions on Learning Technologies. IEEE Computer Society, 2008. Reviewer. [ http ]

Information Systems. Elsevier, 2008. Reviewer. [ http ]

Data and Knowledge Engineering. Elsevier, 2008. Reviewer. [ http ]

Knowledge and Information Systems. Springer, 2008. Reviewer. [ http ]

IEEE Transactions on Dependable and Secure Computing. IEEE Computer Society, 2008. Reviewer. [ http ]

Information Systems. Elsevier, 2007. Reviewer. [ http ]

International Journal of Web and Grid Services (IJWGS). Inderscience, 2007. Reviewer. [ http ]

Journal of Educational Technology and Society (endorsed by IEEE Technical Committee on Learning Technology), 2007. Executive Peer-Reviewer. [ http ]

Journal of Web Semantics. Elsevier, 2006. Reviewer. [ http ]

Journal of Systems and Software. Elsevier, 2006. Reviewer. [ http ]

ACM Journal on Transactions on Internet Technology. ACM, 2006. Reviewer. [ http ]

Journal of Web Semantics. Special Issue on Semantic Grid. Elsevier, 2006. Reviewer. [ http ]

International Semantic Web Conference In-Use Track, Bonn, Germany, October 2011. Program Committee. [ http ]

European Intelligence and Security Informatics Conference (EISIC), Athens, Greece, September 2011. Program Committee. [ http ]

Personal Semantic Data on the Desktop and on the Web in conjunction with the 6th International Conference on Knowledge Capture, Banff, Canada, June 2011. Program Committee. [ http ]

International Semantic Web Conference In-Use Track, Shangai, China, November 2010. Program Committee. [ http ]

Personal Semantic Data(PSD 2010), Lisbon, Portugal, October 2010. Program Committee. [ http ]

BlogTalk 2010), Galway, Ireland, August 2010. Program Committee. [ http ]

IEEE International Policies for Distributed Systems and Networks (POLICY 2010), George Mason University, USA, July 2010. IEEE Computer Society. Program Committee. [ http ]

Linking of User Profiles and Applications in the Social Semantic Web (LUPAS) at the Extended Semantic Web Conference (EWSC 2010), Heraklion, Greece, May 2010. Program Committee. [ http ]

Adaptation, Personalization and REcommendation in the Social-semantic Web (APRESW) at the Extended Semantic Web Conference (EWSC 2010), Heraklion, Greece, May 2010. Program Committee. [ http ]

18th International Conference on User Modeling, Adaptation and Personalization (Industry Track), Hawaii, USA, June 2010. Program Committee. [ http ]

24th AAAI Conference on Artificial Intelligence (AI and the Web Track), Atlanta, Georgia, USA, July 2010. Program Committee. [ http ]

Extended Semantic Web Conference (ESWC) (Social Web Track), Heraklion, Greece, May 2010. Program Committee. [ http ]

International Conference on Grid and Pervasive Computing (GPC), Hualien, Taiwan, May 2010. Program Committee. [ http ]

25th Symposium On Applied Computing(SAC) Privacy on the Web Track, Sierre, Switzerland, March 2010. Program Committee. [ http ]

User Data Interoperability in the Social Web (UDISW) at the International Conference on Intelligent User Interfaces (IUI 2010), Hong Kong, China, February 2010. Program Committee. [ http ]

4th Asian Semantic Web Conference, Shanghai, China, December 2009. Program Committee. [ http ]

International Semantic Web Conference In-Use Track, Washington, USA, October 2009. Program Committee. [ http ]

First International Workshop on Living Web: Making Web Diversity a true asset collocated with the 8th International Semantic Web Conference ISWC-2009, Washington, USA, October 2009. Program Committee. [ .html ]

European Workshop on Combining Context with Trust, Security, and Privacy, co-located with EuroPKI 2009 and ISC 2009, Pisa, Italy, September 2009. Program Committee. [ http ]

Trust, Risk, Reputation and Recommendation on the Web (TR4WEB) in conjuction with 13th East-European Conference on Advances in Databases and Information Systems (ADBIS), Riga, Latvia, September 2009. Program Committee. [ http ]

Joint Workshop Context-Awareness Trust and Web 2.0 Trust (CAT09 2.0) co-located with 3rd IFIP WG 11.11 International Conference on Trust Management (IFIPTM'2009), Purdue, West Lafayette, USA, June 2009. Program Committee.

European Semantic Web Conference In-Use Track, Heraklion, Greece, June 2009. Program Committee. [ http ]

European Semantic Web Conference PhD Symposium, Heraklion, Greece, June 2009. Program Committee. [ http ]

6th European Semantic Web Conference, Lecture Notes in Computer Science, Crete, Greece, June 2009. Springer. Program Committee. [ http ]

International Conference on Grid and Pervasive Computing (GPC), Geneva, Switzerland, May 2009. Program Committee. [ http ]

5th Workshop on Semantic Web and Application Perspectives (SWAP), Roma, Italy, December 2008. Program Committee. [ http ]

3rd Asian Semantic Web Conference, Bangkok, Thailand, December 2008. Program Committee. [ http ]

2nd International Workshop on Combining Context with Trust, Security, and Privacy (CAT'08) co-located with Joint iTrust and PST Conferences on Privacy, Trust Management and Security (IFIPTM'2008), Trondheim, Norway, June 2008. Program Committee. [ http ]

17th International World Wide Web Conference, Posters Track, Beijing, China, April 2008. Program Committee. [ .html ]

IEEE 11th International Conference on Computational Science and Engineering, São Paulo,Brazil, July 2008. IEEE Computer Society. Program Committee. [ .html ]

European Semantic Web Conference PhD Symposium, Tenerife, Spain, June 2008. Program Committee. [ .html ]

5th European Semantic Web Conference, Lecture Notes in Computer Science, Tenerife, Spain, June 2008. Springer. Program Committee. [ http ]

International Conference on Grid and Pervasive Computing (GPC), Kunming, China, May 2008. Program Committee. [ http ]

4th ACM Symposium on Applied Computing (SAC) Trust, Recommendations, Evidence and other Collaboration Know-how (TRECK) Track, Fortaleza, Brazil, March 2008. Program Committee. [ http ]

4th Italian Semantic Web Workshop on Semantic Web Applications and Perspectives (SWAP), Bari, Italy, December 2007. Program Committee. [ http ]

Berliner XML Tage 2007 (BXML'07), Berlin, Germany, September 2007. Program Committee. [ http ]

International Workshop on Combining Context with Trust, Security, and Privacy (CAT'07) co-located with Joint iTrust and PST Conferences on Privacy, Trust Management and Security (IFIPTM2007), Moncton, New Brunswick, Canada, July 2007. Program Committee. [ http ]

22nd AAAI Conference on Artificial Intelligence (special track on AI and the Web), Vancouver, Canada, July 2007. Program Committee. [ http ]

International Workshops on Electronic Games and Personalized eLearning Processes (EGAEL), Nijmegen, The Netherlands, July 2007. Program Committee. [ http ]

4th International Conference on Autonomic and Trusted Computing (ATC-07), Lecture Notes in Computer Science, Hong Kong, China, July 2007. Springer. Program Committee. [ http ]

4th European Semantic Web Conference, Lecture Notes in Computer Science, Inssbruck, Austria, June 2007. Springer. Program Committee. [ http ]

International Conference on Grid and Pervasive Computing (GPC), Paris, France, May 2007. Program Committee. [ http ]

3rd Italian Semantic Web Workshop on Semantic Web Applications and perspectives (SWAP), Pisa, Italy, December 2006. Program Committee. [ http ]

International Conference on Parallel and Distributed Processing and Applications (ISPA 2006), Lecture Notes in Computer Science, Sorrento, Italy, December 2006. Springer. Program Committee. [ http ]

International Conference on Systems and Networks Communications (ICSNC06), Tahiti, French Polynesia, November 2006. Program Committee. [ .html ]

7th IEEE International Conference on Grid Computing, Barcelona, Spain, September 2006. Program Committee. [ http ]

Berliner XML Tage 2006 (BXML'06), Berlin, Germany, September 2006. Program Committee. [ http ]

Workshop on Security and Trust Management (STM) in conjunction with the 11th European Symposium On Research In Computer Security (ESORICS), Hamburg, Germany, September 2006. Program Committee.

3th European Semantic Web Conference, Lecture Notes in Computer Science, Budva, Montenegro, June 2006. Springer. Program Committee. [ http ]

IEEE International Symposium on Circuits and Systems (ISCAS 2006). Special session on Advances in semantic multimedia analysis for personalised content access, Island of Kos, Greece, May 2006. Program Committee. [ http ]

Reasoning on the Web Workshop (RoW2006) in conjunction with the 15th International World Wide Web Conference, Edinburgh, UK, May 2006. Program Committee. [ http ]

2nd Italian Semantic Web Workshop on Semantic Web Applications and perspectives (SWAP), Trento, Italy, December 2005. Program Committee. [ http ]

Semantic Web and Policy Workshop (SWPW) in conjunction with the 4th International Semantic Web Conference, Galway, Ireland, November 2005. Program Committee. [ http ]

Berliner XML Tage 2005 (BXML'05), Berlin, Germany, September 2005. Program Committee. [ http ]

Workshop on Decentralized, Agent Based and Special Approaches to User Modelling (DASUM'05) in conjunction with the 10th International Conference on User Modelling, Edinburgh, UK, July 2005. Program Committee. [ http ]

Asian Semantic Web School, Bangkok, Thailand, December 2008. Lecturer. [ http ]

“Rule-Based Policy Representation and Reasoning for the Semantic Web” in the Reasoning Web Summer School, Dresden, Germany, September 2007. Lecturer. [ http ]

KnowledgeWeb PhD Symposium, Innsbruck, Austria, June 2007. Scientific Advisor. [ http ]

8th IEEE International Workshop on Policies for Distributed Systems and Networks (POLICY 2007), Bologna, Italy, June 2007. Referee. [ http ]

Trust and Security in Learning Networks. In Learning Networks in Practice Conference, organized by the Master of Science programme in Active Learning and the Learning Technology Development Programme of the Educational Technology Expertise Centre. Open University Netherlands, Distance Learning, May 2007. Lecturer. [ http ]

“Introduction to the Semantic Web” in The TENCompetence Winter School, Innsbruck, Austria, January 2007. Lecturer. [ http ]

RuleML International Conference Tutorial on Semantic Web Policies: Where are we and What is still missing?, Athens, Georgia, USA, November 2006. [ .html ]

2nd International Workshop on Automated Specification and Verification of Web Systems, Cyprus, November 2006. Referee. [ http ]

KnowledgeWeb PhD Symposium, Budva, Montenegro, June 2006. Scientific Advisor. [ http ]

European Semantic Web Conference Tutorial on Semantic Web Policies: Where are we and What is still missing?, Budva, Montenegro, June 2006. [ .html ]

4th Workshop on Principles and Practice of Semantic Web Reasoning, Lecture Notes in Computer Science, Budva, Montenegro, June 2006. Springer. Referee. [ http ]

4th International Semantic Web Conference, Lecture Notes in Computer Science, Galway, Ireland, November 2005. Springer. Referee. [ http ]

International Conference on Rules and Rule Markup Languages for the Semantic Web (RuleML-2005), Galway, Ireland, November 2005. Referee. [ http ]

World Conference on ELearning in Corporate, Government, Healthcare, & Higher Education (ELearn), Vancouver, Canada, October 2005. Association for the Advancement of Computing in Education (AACE). Referee. [ http ]

Workshop on Peer-to-Peer Knowledge Management (P2PKM) colocated with the 2nd Annual International Conference on Mobile and Ubiquitous Systems: Networking and Services (MobiQuitous 2005), San Diego, US, July 2005. Referee. [ http ]

European Academic Software Award 2004 (EASA 2004), 2004. Member of the Jury. [ http ]