Editorial Board member of Computer Supported Cooperative Work: The Journal of Collaborative Computing JCSCW, Springer-Verlag, Heidelberg, Germany. (ISSN Online 1573-7551, ISSN Print: 0925-9724).

Editorial Board member of the International Journal of Ambient Intelligence and Humanised Computing JAIHC, Springer-Verlag, Heidelberg, Germany. (ISSN Online: 1868-5145, ISSN Print: 1868-5137).

Editorial Board member of the International Journal of Autonomous and Adaptive Communications Systems IJAACS, Inderscience Publishers, Geneva, Switzerland. (ISSN Online: 1754-8640, ISSN Print: 1754-8632).

Editorial Board member of the International Journal of Arts and Technology IJART, Inderscience Publishers, Geneva, Switzerland. (ISSN Online): 1754-8861, ISSN Print: 1754-8853)

Editorial Board member of the Journal of Cases on Information Technology JCIT, IGI Global (formerly "Idea Group Inc.") (ISSN: 1548-7717, EISSN: 1548-7725).

Editorial Board member of the Journal of Information Technology Research JITR, IGI Global (formerly "Idea Group Inc.") (ISSN: ISSN: 1938-7857, EISSN: 1938-7865).

Editorial Board member of the Open Ergonomics Journal, Bentham Science Publishers (ISSN: 1874-9216).

Editorial Board member of the i-com Journal of Interactive Media, De Gruyter, Berlin, Germany. (ISSN: 2196-6826).

Associate Chair of the 17th IFIP TC.13 International Conference on Human-Computer Interaction (INTERACT 2019), in Paphos, Cyprus, on September 2 to 6.

Exploratory Papers Co-Chair of the 16th European Conference on Computer-Supported Cooperative Work (ECSCW 2018), in Nancy, France, on June 4 to 8--together with Michael Muller (IBM Research Cambridge, USA).

Associate Chair of the 16th IFIP TC.13 International Conference on Human-Computer Interaction (INTERACT 2017), in Mumbai, India, on September 25 to 29.

General Co-Chair of the Fifteenth IFIP TC.13 International Conference on Human-Computer Interaction (INTERACT 2015), in Bamberg, Germany, on Sept. 14 to 18--togehter with Julio Abascal (University of Basque Country).

Workshop Co-Chair of the 6th International Conference on Communities and Technologies (C&T 2013), in Munich, Germany, on June 29 to July 2--together with Alessandra Agostini (University of Milano Bicocca).

Program Co-Chair of the International ACM SIGGROUP Conference on Supporting Group Work (Group 2012), in Sanibel Island, Florida, on October 27 to 31--together with Kori Inkpen (Microsoft Research).

Publicity Co-Chair of the 2012 International Conference on Collaboration Technologies and Systems (CTS 2012), in Denver, CO, on May 21 to 25.

Publicity Co-Chair of the 2011 International Conference on Collaboration Technologies and Systems (CTS 2011), in Philadelphia, PA, on May 23 to 27--together with Yong Liu (NCSA, University of Illinois at Urbana-Champaign) and Carlos Westphall (UFSC - Federal University of Santa).

Program Co-Chair of the International ACM SIGGROUP Conference on Supporting Group Work (Group 2010), in Sanibel Island, Florida, on November 7 to 10--together with Madhu Reddy (Penn State University).

Program Co-Chair of the Eighteenth Euromicro Conference on Parallel, Distributed, and Network-Based Processing (PDP 2010), in Pisa, Italy, on February 17 to 19--together with Marco Danelutto (University of Pisa), Julien Bourgeois (University of Franche-Comte).

Publicity Co-Chair of the ACM 2010 Conference on Computer-Supported Cooperative Work (CSCW 2010), in Savannah, Georgia, on February 6 to 10--together with Scott Counts (Microsoft Research).

Program Co-Chair of the Twelfth IFIP TC.13 International Conference on Human-Computer Interaction (INTERACT 2009), in Uppsala, Sweden, on August 24 to 28--together with Paula Kotze (University of South Africa).

General Chair and Program Co-Chair of the Seventeenth Euromicro Conference on Parallel, Distributed, and Network-Based Processing (PDP 2009), in Weimar, Germany, on February 18 to 20--together with Didier El Baz and Francois Spies.

Proceedings Chair of the ACM 2008 Conference on Computer-Supported Cooperative Work (CSCW 2008), in Monterey, California, on November 8 to 12.

Notes Associate Chair of the Conference on Human Factors in Computing Systems (CHI 2008), in Florence, Italy, on April 5 to 10.

General Chair of the International ACM SIGGROUP Conference on Supporting Group Work (Group 2007) on Sanibel Island, Florida, in November 4 to 7--together with Kori Inkpen (Dalhousie University).

Interactive Experience Co-Chair of the Eleventh IFIP TC.13 Internactional Conference on Human-Computer Interaction - (INTERACT 2007) in Rio de Janeiro, Brasil, on September 10 to 14--together with Carlos Scolari (Universitat de Vic).

General Chair and Programme Committee Chair of the Mensch & Computer 2007 (M&C 2007) (German-speaking Human-Computer Interaction Conference) in Weimar, Germany, on September 2 to 5.

Short Papers and Demos Co-Chair at the Tenth IFIP TC.13 Internactional Conference on Human-Computer Interaction (INTERACT 2005) in Rome, Italy, on September 12 to 16--together with Luca Chittaro (University of Udine).

Tutorial Co-Chair of the Mensch & Computer 2004 (M&C 2004) (German-speaking Human-Computer Interaction Conference), in Paderborn, Germany, on September 5 to 8--together with Wolfgang Mueller (c-lab Paderborn).

HCI Overviews Co-Chair at the Conference on Human Factors in Computing Systems (CHI 2004) in Vienna, Austria, on April 24 to 29--together with Julie Jacko (Georgia Tech).

Tutorial Co-Chair of the Mensch & Computer 2003 - Interaktion in Bewegung (M&C 2003) (German-speaking Human-Computer Interaction Conference) in Stuttgart, Germany, on September 7 to 10.

Workshop Co-Chair at the Nineth IFIP TC.13 Internactional Conference on Human-Computer Interaction (INTERACT 2003), in Zurich, Switzerland, on September 1 to 5--together with Philippe Palanque.

Short Talk Associate Co-Chair of the Conference on Human Factors in Computing Systems (CHI 2003), in Fort Lauderdale, Florida, on April 5 to 10.

General Co-Chair of the Stream 9 on Usability: Gaining a Competitive Edge at the IFIP World Computer Congress (WCC2002) in Montreal, Canada, on August 25th to 30th--together with Judy Hammond and Janet Wesson.

Short Talks & Interactive Posters Co-Chair at the Conference on Human Factors in Computing Systems (CHI 2002) in Minneaplolis, Minnesota, on April 20th to 25th--together with Marilyn Salzman (Genomica).

Tutorial Co-Chair at the European Conference on Computer-Supported Cooperative Work (ECSCW 2001), in Bonn, Germany, on September 16th to 20th--together with Peter Carstensen (IT University, Kopenhagen).

Student Volunteer Co-Chair at the Conference on Human Factors in Computing Systems (CHI 2000) in The Hague, The Netherlands, on April 1 to 6--together with Garett Dworman (University of Pennsylvania, Philadelphia).

Student Poster Co-Chair at the Conference on Human Factors in Computing Systems (CHI'99) in Pittsburgh, PE, on May 15 to 20--together with Kori Inkpen (Simon Fraser University, Vancouver).

Workshop Co-Organiser of the Workshop on Human(s) in the Loop – Bringing AI & HCI Together at the 17th IFIP TC13 International Conference on Human-Computer Interaction (INTERACT 2019), in Paphos, Cyprus, on September 2 to 6.

Workshop Co-Organiser of the Workshop on Group Recommender Systems: Concepts, Technology, Evaluation (GroupRS) at the 21st Conference on User Modeling, Adaptation and Personalisation (UMAP 2013), in Rome, Italy, on June 10 to 14.

Doctoral Consortium Co-Chair of the Mensch & Computer 2012 (M&C 2012), in Konstanz, Germany, on September 9 to 12.

Workshop Co-Organiser of the Workshop Supporting Asynchronous Collaboration in Visual Analytics Systems at the International Conference on Advanced Visual Interfaces (AVI 2012), in Capri, Italy, on May 21 to 25.

Workshop Co-Organiser of the 1st International Workshop on Enhancing Learning with Ambient Displays and Visualization Techniques (ADVTEL 2011), in Palermo, Italy, on September 20 to 21; in conjunction with the 6th European Conference on Technology Enhanced Learning (EC-TEL 2011).

Workshop Co-Organiser of the Workshop Mobile HCI and Technical ICTD: A Methodological Perspective at the Mobile Hunan-Computer Interaction (MobileHCI 2010), in Lisbon, Portugal, on September 7 to 10.

Workshop Co-Organiser of the Workshop on Mind the Gap - Towards Seamless Remote Social Interaction at the Advanced Visual Interfaces (AVI 2010), in Rome, Italy, on May 25 to 29.

Special Session Organiser on Computer-Supported Cooperative Work at the Seventeenth International Information Management Talks (IDIMT 2009), in Jindrichuv Hradec, Czech Republic, on September 9 to 11.

Special Session Organiser on Cooperative Information Environments at the Fiveteenth International Information Management Talks (IDIMT 2007), in Budweis, Czech Republic, on September 12 to 14.

Special Session Organiser on Cooperative Information Environments at the Thirteenth International Information Management Talks (IDIMT 2005), in Budweis, Czech Republic, on September 14 to 16.

Special Session Organiser on Cooperative Information Environments at the Eleventh International Information Management Talks (IDIMT 2003), in Zadov, Czech Republic, on September 10 to 12.

Special Session Organiser on Cooperative Information Environments at the Ninth International Information Management Talks (IDIMT 2001), in Zadov, Czech Republic, on September 19 to 21.

Workshop Organiser of the Workshop on User Modelling for Context-Aware Applications at the 8th International Conference on User Modeling (UM 2001), in Sonthofen, Germany, on July 13 to 17---together with Marcus Specht, GMD-FIT.

Workshop Co-Organiser of the Workshop WAP - Interaktionsdesign und Bentutzbarkeit at the Mensch & Computer 2001 (M&C 2001) in Bad Honnef, Germany, on March 5 to 8---together with Albrecht Schmidt (TecO Karlsruhe) and Oli Frick (SAP Karlsruhe)).

Special Session Organiser on Web Computing at the Euromicro Workshop on Parallel and Distributed Processing (PDP 2001), in Mantova, Italy, on Februar 17 to 19.

Special Session Organiser on Cooperative Web Computing at the Eighth International Information Management Talks (IDIMT 2000), in Zadov, Czech Republic, on September 20 to 22.

Organising Committee member of the European Conference on Object-Oriented Programming (ECOOP'96) in Linz, Austria.

Student Volunteer the Conference on Human Factors in Computing Systems (CHI'95, CHI'96, CHI'97), at the Conference on Computer-Supported Cooperative Work (CSCW'96), at the European Conference on Computer-Supported Cooperative Work (ECSCW95, ECSCW97), and at the World Conference on Educational Multimedia and Hypermedia (ED-MEDIA'95)

Programme Committee member of the Track Computer-Supported Cooperative Work and Social Computing at the Multikonfernz Wirtschaftsinformatik (MKWI 2018) in Lueneburg, Germany, on March 6 to 9.

Programme Committee member of the 2018 International ACM Conference on Supporting Group Work (Group 2018), on Sanibel Island, Florida, on January 7 to 10.

Programme Committee member of the Mensch & Computer 2017 (M&C 2017), in Regensburg, Germany, on September 10 to 13.

Programme Committee member of the Fiveteenth European Conference on Computer-Supported Cooperative Work (ECSCW 2017) in Sheffield, UK, on August 28 to September 1.

Programme Committee member of the Track Interaktionen und Interfaces (Interactions and Interfacesn) at the Multikonfernz Wirtschaftsinformatik (MKWI 2017) in St. Gallen, Switzerland, on February 12 to 15

Programme Committee member of the Track Computer-Supported Cooperative Work and Social Computing at the Multikonfernz Wirtschaftsinformatik (MKWI 2016), in Ilmenau, Germany, on March 9 to 11.

Programme Committee member of the Fourteenth European Conference on Computer-Supported Cooperative Work (ECSCW 2015), in Oslo, Norway, on September 19 to 23.

Programme Committee member of the 2014 International ACM Conference on Supporting Group Work (Group 2014), on Sanibel Island, Florida, on November 9 to 12.

Programme Committee member of the Eleventh International Conference on the Design of Cooperative Systems (COOP 2014), in Nice, France, on May 27 to 30.

Programme Committee member of the 16th International Conference on Enterprise Information Systems (ICEIS 2014), in Lisbon, Portugal, on April 27 to 30.

Programme Committee member of the Track Kooperationssyssteme (Cooperation Systems) at the Multikonfernz Wirtschaftsinformatik (MKWI 2014), in Paderborn, Germany, on February 26 to 28.

Programme Committee member of the Thirteenth European Conference on Computer-Supported Cooperative Work (ECSCW 2013), in Paphos, Cyprus, on September 21 to 25.

Programme Committee member of the Mensch & Computer 2013 (M&C 2013), in Bremen, Germany, on September 8 to 11.

Programme Committee member of the 14th IFIP TC13 International Conference on Human-Computer Interaction (INTERACT 2013), in Cape Town, South Africa, on September 2 to 6.

Programme Committee member of the 2013 International Conference on Collaboration Technologies and Systems (CTS 2013), in San Diego, CA, on May 20 to 24.

Programme Committee member of the ACM Conference on Tangible, Embedded and Embodied Interaction (TEI 2013), in Barcelona, Spain, on February 10 to 13.

Programme Committee member of the 18th Collaboration Research International Working Group Conference on Collaboration and Technology (CRIWG 2012), in Duisburg, Germany, on September 16 to 19.

Programme Committee member of the Mensch & Computer 2012 (M&C 2012), in Konstanz, Germany, on September 9 to 12.

International Techncal Programme Committee member of the 2012 International Conference on Collaboration Technologies and Systems (CTS 2012), in Denver, CO, on May 21 to 25.

Programme Committee member of the Track Kooperationssyssteme (Cooperation Systems) at the Multikonfernz Wirtschaftsinformatik (MKWI 2012), in Braunschweig, Germany, on February 29 to March 2.

Programme Committee member of the ACM Conference on Tangible, Embedded and Embodied Interaction (TEI 2012), in Kingston, Canada, on February 19 to 22.

Programme Committee member of the 17th Collaboration Research International Working Group Conference on Collaboration and Technology (CRIWG 2011), in Paraty, Rio de Janeiro, Brazil, on October 2 to 7.

Programme Committee member of the 1st International Workshop on Enhancing Learning with Ambient Displays and Visualisation Techniques (ADVTEL 2011), on September 20 to 21, in conjunction with the 6th European Conference on Technology Enhanced Learning (EC-TEL 2011), in Palermo, Italy, on September 20 to 23.

Associate Chair and Programme Committee member of the 13th IFIP TC13 International Conference on Human-Computer Interaction (INTERACT 2011), in Lissbon, Portugal, on September 5 to 9.

Programme Committee member of the Twelfth European Conference on Computer-Supported Cooperative Work (ECSCW 2011), in Aarhus, Denmark, on September 24 to 28.

Programme Committee member of the Mensch & Computer 2011 (M&C 2011), in Chemnitz, Germany, on September 11 to 14.

Scientific Committee member of the IADIS International Conference on Interfaces and Human Computer Interaction (IHCI 2011), in Rome, Italy, on July 24 to 26.

International Techncal Programme Committee member of the 2011 International Conference on Collaboration Technologies and Systems (CTS 2011), in Philadelphia, PA, on May 23 to 27.

Programme Committee member of the 10. Internationale Tagung Wirtschaftsinformatik - (Wirtschaftsinformatik 2011), in Zurich, Switzerland, on February 16 to 18.

Programme Committee member of the Special Session on Next Generation of Web Computing at the 19th EUROMICRO Conference on Parallel, Distributed, and Network-Based Processing (PDP 2011), in Ayia Napa, on February 9 to 11.

Programme Committee member of the ACM Conference on Tangible, Embedded and Embodied Interaction (TEI 2011), in Funchal, Madeira, on January 23 to 26.

Programme Committee member of the 2nd IFIP International Human-Computer Interaction Symposium of the World Computer Congress (WCC 2010), in Brisbane, Australia, on September 20 to 23.

Programme Committee member of the ACM Conference on Tangible and Embedded Interaction (TEI 2010), in Cambridge, MA, on January 25 to 27.

Programme Committee member of the International Conference on Arts & Technology (ArtsIT 2009), in Yi-Lan, Taiwan, on September 24 to 25.

Programme Committee member of the 11th International Conference on Human Computer Interaction with Mobile Devices and Services (Mobile HCI 2009), in Bonn, Germany, on September 15 to 18.

Programme Committee member of the Eleventh European Conference on Computer-Supported Cooperative Work (ECSCW 2009), in Vienna, Austria, on September 7 to 11.

Programme Committee member of the International Symposium on Collaborative Technologies and Systems (CTS 2009), in Balitmore, Maryland, on May 18 to 22.

Programme Committee member of the Mensch & Computer 2009 (M&C 2009), in Berlin, Germany, on September 6 to 9.

Programme Committee member of the Special Session on Next Generation of Web Computing at the 35th EUROMICRO Conference on Software Engineering and Advanced Applications (SEAA 2009), in Patras, Greece, on August 27 to 29.

Programme Committee member of the 2009 International ACM Conference on Supporting Group Work (Group 2009), in Sanibel Island, Florida, on May 10 to 13.

Programme Committee member of the Third International Conference on Tangible and Embedded Interaction (TEI 2009), in Cambridge, UK, on February 16 to 18.

Programme Committee member of the Third International Conference on Computer Graphics Theory and Applications (GRAPP 2009), in Lisbon, Portual, on February 5 to 8.

Programme Committee member of the ACM International Conference on Multimedia (Multimedia 2008), in Vancouver, Canada, on October 27 to November 1.

Programme Committee member of the Annual International Conference of the South African Institute of Computer Scientists and Information Technologists (SAICSIT 2008), in Garden Route, Wilderness, South Africa, on October 6-8.

Programme Committee member of the Workshop Mobile and Embedded Interactive Systems (MEIS 2008) at the 38. Jahrestagung der Geselleschaft fuer Informatik (INFORMATIK 2008), in Munich, Germany, on 8 to 13 September.

Programme Committee member of the Workshop on Adaptive Collaboration Support at the 5th International Conference on Adaptive Hypermedia & Adaptive Web-based Systems (AH2008), in Hannover, Germany, on July 28.

Programme Committee member of the Eigth International Conference on the Design of Cooperative Systems (COOP 2008), in Carry-le-Rouet, France, on May 20 to 23.

Programme Committee member of the International Symposium on Collaborative Technologies and Systems (CTS 2008), in Irvine, California, on May 19 to 23.

Programme Committee member of the Usability Day VI, in Dornbirn, Austria, on May 16.

Programme Committee member of the 2nd International Conference on Tangible and Embedded Interaction (TEI 2008), in Bonn, Germany, on February 16 to 18.

Programme Committee member of the Conference on "Kooperationssysteme / Cooperation Systems" at the Multi-Conference Wirtschaftsinformatik (MKWI 2008), in Munich, Germany, on February 26 to 28.

Programme Committee member of the Sixtenth Euromicro Conference on Parallel, Distributed, and Network-Based Processing (PDP 2008), in Toulouse, France, on February 13 to 15.

Programme Committee member of the Third International Conference on Computer Graphics Theory and Applications (GRAPP 2008), in Funchal, Madeira Island, Portugal, on January 22 to 25.

Programme Committee member of the 6th International Conference on Mobile and Ubiquitous Multimedia (MUM 2007), in Oulu, Finland, on December 12 to 14.

Programme Committee member the European Conference on Ambient Intelligence (AmI 2007), in Darmstadt, Germany, on November 7 to 10.

Programme Committee member the Annual International Conference of the South African Institute of Computer Scientists and Information Technologists (SAICSIT 2007), in Fish River Sun, Eastern Cape, South Africa, September 30 to October 3.

Programme Committee member of the 13th International Workshop on Groupware (CRIWG 2007), in Bariloche, Argentina, on Sept. 16-20.

Programme Committee member of the Special Session on Next Generation of Web Computing at the 33rd EUROMICRO Conference on Software Engineering and Advanced Applications (SEAA 2007), in Luebeck, Germany, on Aug. 27 to 31.

Programme Committee member of the International Conference on Intelligent Multimedia and Ambient Intelligence (IMAI 2007), in Salt Lake City, Utah, on July 15 to 22.

Programme Committee member of the 2nd Workshop on Tangible Interaction in Collaborative Environments (TICE), at the IEEE 16th International Workshops on Enabling Technologies Infrastructures for Collaborative Enterprises WETICE 2007, in Paris, France, on June 18 to 20.

Programme Committee member of the the 5th UMICS 2007 International Workshop on Ubiquitous Mobile Information and Collaboration Systems at the 19th International Conference on Advanced Information Systems Engineering (CAiSE 2007), in Trondheim, Norway, on June 11 to 12.

Programme Committee member of the Workshop on Application and Security Service in Intelligent Environments 2007 (ASSIE 2007) at the International Conference on Computational Science: Advancing Science and Society Through Computation, in Beijing, China, on May 27 to 30.

Programme Committee member of the International Symposium on Collaborative Technologies and Systems (CTS 2007), in Orlando, Florida, on May 21 to 25.

Programme Committee member of the Annual International Conference of Human-Computer Interaction Educators (HCI Educators 2007), in Aveiro, Portugal, on March 29 to 30.

Programme Committee member of the IASTED European Conference on Internet and Multimedia Systems and Applications (EuroIMSA 2007), in Chamonix, France, March 14 to 16.

Programme Committee member of the 2nd International Conference on Computer Graphics Theory and Applications (GRAPP 2007), in Barcelona, Spain, on March 8 to 11.

Programme Committee member of the 1st International Conference on Tangible and Embedded Interaction (TEI 2007), in Baton Rouge, Louisiana, on February 15 to 17.

Programme Committee member of the ACM 2006 Conference on Computer-Supported Cooperative Work (CSCW 2006), in Banff, Canada, on November 4 to 8.

Programme Committee member of the Workshop on Koordination in verteilten Entwicklungsprojekten - Anforderungen, Erfahrungen, Praxisberichte (Coordination in Distributed Development Projects - Requirements, Experience, Reports; in German), at the 36. Jahrestagung der Geselleschaft fuer Informatik (INFORMATIK 2006), in Dresden, Germany, on October 2 to 6.

Programme Committee member of the Workshop Mobile and Embedded Interactive Systems (MEIS'06), at the 36. Jahrestagung der Geselleschaft fuer Informatik (INFORMATIK 2006), in Dresden, Germany, on October 2 to 6.

Programme Committee member of the Mensch & Computer 2006 (M&C 2006), in Gelsenkirchen, Germany, on September 3 to 6.

Programme Committee member of the Special Session on Next Generation of Web Computing at the 32nd EUROMICRO Conference on Software Engineering and Advanced Applications (SEAA 2006), in Cavtat, Dubrovnik, Croatia, on August 29 to September 1.

Programme Committee member of the Workshop on Tangible Interaction in Collaborative Environments (TICE), at the IEEE 15th International Workshops on Enabling Technologies Infrastructures for Collaborative Enterprises (WETICE 2006), in Manchester, UK, on June 26 to 28.

Programme Committee member of the Fourteenth IEEE International Workshop on Quality of Service (IWQoS 2006), at the Yale University in New Haven, CT, on June 19 to 21.

Programme Committee member of the Usability Day IV, in Dornbirn, Austria, on June 9.

Programme Committee member of the 4th UMICS 2006 workshop at the 18th International Conference on Advanced Information Systems Engineering (CAiSE 2006), in Luxembourg, Grand-Duchy of Luxembourg, on June 5 to 7.

Programme Committee member of the Third International Workshop on Computer-Supported Activity Coordination (CSAC 2006), in Paphos, Cyprus, on May 23 to 24.

Programme Committee member of the 7th International Conference on the Design of Cooperative Systems (COOP 2006), in Carry-le-Rouet, France, on May 9 to 12.

Programme Committee member of the Conference 'Collaborative Business' at the Multi-Conference Wirtschaftsinformatik 2006 (MKWI 2006), in Passau, Germany. on February 20 to 22.

Programme Committee member of the Special Session on 'Web Computing' of the Fourteenth Euromicro Conference on Parallel, Distributed nad Network-based Processing (PDP 2006), in Montbeliard, France, on February 15 to 17.

Programme Committee memberof the Fourth International Conference on Mobile and Ubiquitous Multimedia - MUM 2005, in Christchurch, New Zealand, on December 8 to 10.

Programme Committee member of the IASTED International Conference on Human-Computer Interaction (IASTED- HCI 2005), in Phoenix, AZ, on November 14 to 16.

Programme Committee member of the IADIS International Conference (WWW/Internet 2005), in Lisbon, Portugal, on October 19 to 22.

Programme Committee member of the Workshop 'Kooperationssysteme' at the 35. Jahrestagung der Gesellschaft fuer Informatik e.V. (INFORMATIK 2005), in Bonn, Germany, on September 19 to 21. (in German).

Programme Committee member of the Nineth European Conference on Computer-Supported Cooperative Work (ECSCW 2005), in Paris, France, on September 18 to 22.

Programme Committee member of the Mensch & Computer 2005 (M&C 2005), in Linz, Austria, on September 4 to 7.

Programme Committee member of the Special Session on Next Generation of Web Computing at the 31st EUROMICRO Conference on Software Engineering and Advanced Applications (SEAA 2005), in Porto, Portugal, on August 30 to September 3.

Programme Committee member of the 3rd UMICS 2005 workshop at the 17th International Conference on Advanced Information Systems Engineering (CAiSE), in Porto, Portugal, on June 13 to 17.

Programme Committee member of the International Workshop on Evaluation of Collaborative Information Systems and Support for Virtual Enterprises at the IEEE 14th International Workshops on Enabling Technologies: Infrastructures for Collaborative Enterprises (WETICE 2005), in Linkoping University, Sweden, on June 13 to 15.

Programme Committee member the Second International Workshop on Computer-Supported Activity Coordination (CSAC 2005), in Miami, FL, on May 24 to 25.

Programme Committee member of the 1st International Workshop on Exploiting Context Histories in Smart Environments (ECHISE 2005), in Munich, Germany, on May 11, at the 3rd International Conference on Pervasive Computing - PERVASIVE 2005.

Programme Committee member of the Special Session on 'Advances in Web Computing' of the Thirteenth Euromicro Conference on Parallel, Distributed nad Network-based Processing (PDP 2005), in Lugano, CH, on February 9 to 11.

Programme Committee member of the Third International Conference on Mobile and Ubiquitous Multimedia (MUM 2004), in College Park, Maryland, on October 27 to 29.

Programme Committee member of the IADIS International Conference (WWW/Internet 2004), in Madrid, Spain, on October 6 to 9.

Programme Committee member of the Sixth International Conference on Human-Computer Interaction with Mobile Devices and Services (Mobile HCI 2004), in Glasgow, UK, on September 13 to 16.

Programme Committee member of the Mensch & Computer 2004 (M&C 2004), in Paderborn, Germany, on September 5 to 8.

Programme Committee member of the 3rd International Conference on Entertainment Computing (ICEC 2004), in Eindhoven, NL, on September 1 to 3.

Programme Committee member of the Special Session on Advances in Web Computing at the Euromicro 2004 Conference, in Rennes, France, on August 31 to September 3.

Programme Committee member of the Workshop on Evaluation of Collaborative Information Systems and Support for Virtual Enterprises at the IEEE 13th International Workshops on Enabling Technologies: Infrastructures for Collaborative Enterprises (WETICE 2004) in Modena, Italy, on June 14 to 16.

Programme Committee member of the European Conference on Computer-Supported Cooperative Work (ECSCW 2003) in Helsinki, Finland, on September 14 to 18.

Programme Committee member of the Fifth International Symposium on Human-Computer Interaction with Mobile Devices and Services (Mobile HCI 2003) in Udine, Italy, on September 8 to 11.

Programme Committee member of the Workshop on Evaluation of Collaborative Information Systems and Support for Virtual Enterprises at the IEEE 12th International Workshop on Enabling Technologies: Infrastructures for Collaborative Enterprises (WETICE 2003), in Linz, Austria, on June 9 to 11.

Programme Committee member of the First International Conference on Mobile and Ubiquitous Multimedia (MUM 2002) in Oulu, Finland, on December 12 to 14.

Programme Committee member of the Fourth International Symposium on Human-Computer Interaction with Mobile Devices (Mobile HCI 2002) in Pisa, Italy on September 18 to 20.

Programme Committee member of the Mensch & Computer 2002 - Vom interaktiven Werkzeug zu kooperativen Arbeits- und Lernwelten (M&C 2002) in Hamburg, Germany, on September 2 to 5.

Programme Committee member of the IFIP Conference On Human-Computer Interaction (INTERACT'99) in Edinburth, Scotland.

I have been Reviewer for several international journals, conferences, and books in the areas of Computer-Supported Cooperative Work, Human-Computer Interaction, Ubiquitous Computing, and so forth.