Welcome to the 6th International Conference on Open Source Systems of the IFIP Working Group 2. 13. This year was the ?rst time this international conf- ence was held in North America. We had a large number of high-quality papers, highlyrelevantpanelsandworkshops, acontinuationofthepopulardoctoralc- sortium, and multiple distinguished invited speakers. The success of OSS 2010 was only possible because an Organizing Committee, a Program Committee, Workshop and Doctoral Committees, and authors of research manuscripts from over 25 countries contributed their time and interest to OSS 2010. In the spirit of the communities we study, you self-organized, volunteered, and contributed to this important research forum studying free, libre, open source software and systems. We thank you Despite our modest success, we have room to improve and grow our conf- ence and community. At OSS 2010 we saw little or no participation from large portions of the world, including Latin America, Africa, China, and India. But opportunitiestoexpandarepossible. InJapan, weseeahotspotofparticipation led by Tetsuo Noda and his colleagues, both with full-paper submissions and a workshopon"OpenSourcePolicyandPromotionofITIndustries inEastAsia. " The location of OSS 2011 in Salvador, Brazil, will hopefully result in signi?cant participation from researchers in Brazil - already a strong user of OSS - and otherSouthAmericancountries. UndertheleadershipofMeganSquire, Publicity Chair, we recruited RegionalPublicity Co-chairscovering Japan (Tetsuo Noda), Africa(SulaymanSowe), the MiddleEastandSouthAsia(FaheenAhmed), R- sia and Eastern Europe (Alexey Khoroshilov), Western Europe (Yeliz Eseryel), UK and Ireland (Andrea Capiluppi), and the Nordic countries (Bj] orn Lundell)."

Welcome to the 5th International Conference on Open Source Systems! It is quite an achievement to reach the five-year mark - that's the sign of a successful enterprise. This annual conference is now being recognized as the primary event for the open source research community, attracting not only high-quality papers, but also building a community around a technical program, a collection of workshops, and (starting this year) a Doctoral Consortium. Reaching this milestone reflects the efforts of many people, including the conference founders, as well as the organizers and participants in the previous conferences. My task has been easy, and has been greatly aided by the hard work of Kevin Crowston and Cornelia Boldyreff, the Program Committee, as well as the Organizing Team led by Bjoern Lundell. All of us are also grateful to our attendees, especially in the difficult economic climate of 2009. We hope the participants found the conference valuable both for its technical content and for its personal networking opportunities. To me, it is interesting to look back over the past five years, not just at this conference, but at the development and acceptance of open source software. Since 2004, the business and commercial side of open source has grown enormously. At that time, there were only a handful of open source businesses, led by RedHat and its Linux distribution. Companies such as MySQL and JBoss were still quite small.

Welcome to the 5th International Conference on Open Source Systems! It is quite an achievement to reach the five-year mark - that's the sign of a successful enterprise. This annual conference is now being recognized as the primary event for the open source research community, attracting not only high-quality papers, but also building a community around a technical program, a collection of workshops, and (starting this year) a Doctoral Consortium. Reaching this milestone reflects the efforts of many people, including the conference founders, as well as the organizers and participants in the previous conferences. My task has been easy, and has been greatly aided by the hard work of Kevin Crowston and Cornelia Boldyreff, the Program Committee, as well as the Organizing Team led by Bjoern Lundell. All of us are also grateful to our attendees, especially in the difficult economic climate of 2009. We hope the participants found the conference valuable both for its technical content and for its personal networking opportunities. To me, it is interesting to look back over the past five years, not just at this conference, but at the development and acceptance of open source software. Since 2004, the business and commercial side of open source has grown enormously. At that time, there were only a handful of open source businesses, led by RedHat and its Linux distribution. Companies such as MySQL and JBoss were still quite small.

3. 1 What are formal methods? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3. 2 A survey of formal methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 3. 2. 1 FDTs and FSLs for sequential software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 3. 2. 1. 1 VDM (Vienna Development Method). . . . . . . . . . . . . . . . . . . . . 19 3. 2. 1. 2 Z. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 3. 2. 1. 3 me too . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 3. 2. 1. 4 HOS and AXES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 3. 2. 1. 5 Gist. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 3. 2. 1. 6 Clear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 3. 2. 1. 7 OBJ. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 3. 2. 1. 8 ACT ONE and ACT TWO. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 3. 2. 1. 9 CIP-L. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 3. 2. 1. 10 LPG. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 3. 2. 1. 11 Larch. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 3. 2. 1. 12 Logic languages-the Prolog family. . . . . . . . . . . . . . . . . . . 22 3. 2. 1. 13 Functional languages. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 3. 2. 2 FDTs and FSLs for concurrent software. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 3. 2. 2. 1 LOTOS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 3. 2. 2. 2 Estelle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 3. 2. 2. 3 SDL. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 3. 2. 2. 4 ASN. l . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 3. 2. 2. 5 TTCN. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 3. 2. 2. 6 Gypsy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 3. 2. 3 Graphical formalisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 3. 2. 3. 1 Petri nets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 3. 2. 3. 2 Higraphs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 3. 2. 4 Less formal methods and notations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 3. 2. 4. 1 SADT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 3. 2. 4. 2 Structured Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 3. 2. 4. 3 SSADM and LSDM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 3. 2. 4. 4 JSPandJSD. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 3. 2. 4. 5 HDM and the SPECIAL language . . . . . . . . . . . . . . . . . . . . . . . . . . 27 3. 2. 4. 6 Structured analysis and design of real-time systems. . 27 3. 3 Support tools for FDTs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .