In its classical treatment within philosophy and the social sciences, from Aristotle to the present day, the study of argumentation has focused on ‘human orientated’ uses of argument, such as when an argument can be considered legitimate or flawed, the processes by which participants engage in debate, rhetorical aspects of argumentation etc. However, in the last couple of decades, the study of logic, and more broadly ‘computational’ models of argumentation, has emerged as a growing sub-area of AI. While researchers from a number of fields contributed to this growth, it was those with a background in logics for non-monotonic and uncertain reasoning, and logic based models of argumentation for epistemic reasoning, decision making and dialogue, that fuelled this surge of interest in argumentation. In particular, the first biennial International Conference on Computational Models of Argument (COMMA), was supported by the EU 6th Framework Programme project ASPIC, and was hosted by the University of Liverpool in 2006. Since then a steering committee promoting the continuation of the conference was established, and the subsequent steady growth of worldwide interest in computational argumentation has gone hand in hand with the development of the conference itself, and of related activities. Specifically, plenary invited talks by world-leading researchers, and a software demonstration session, were introduced to the programme in the second edition (COMMA'08) hosted by IRIT in Toulouse. COMMA'10, hosted by the University of Brescia in Desenzano del Garda, saw the addition of a best student paper award, and the same year saw inauguration of a new journal – Argument and Computation – closely related to the COMMA community. The fourth edition, organized by the Vienna University of Technology in 2012, introduced an Innovative Application Track and the proceedings now included a section for Demonstration abstracts. COMMA'14, hosted by the Universities of Aberdeen and Dundee in Pitlochry, was preceded by the first Summer School on Argumentation: Computational and Linguistic Perspectives, while the same year also saw the launch of the first International Competition on Computational Models of Argumentation (ICCMA). The sixth edition of COMMA, organized by the University of Potsdam, included two additional satellite workshops: Systems and algorithms for formal argumentation and Foundations of the language of argumentation.

This year COMMA is hosted by the Institute of Philosophy and Sociology of the Polish National Academy of Sciences in Warsaw, Poland. It is a testament to both the broad multidisciplinary interest in argumentation and the increasing body of work establishing the relevance of computational models to these various disciplines, and in real world applications, that COMMA'18 is one among a number of events constituting the Warsaw Argumentation Week (WAW). Indeed, WAW also includes the Third Summer School on Argumentation: Computational and Linguistic Perspectives, as well as the 16th ArgDiaP Conference on Argumentation and Corpus Linguistics and two colocated workshops on methodologies for research on rhetoric and methodologies for research on legal argumentation.

The COMMA'18 programme reflects the broad reach and burgeoning interdisciplinary focus and application uses of computational models of argument. COMMA'18 includes the second edition of the workshop Systems and algorithms for formal argumentation, as well as the additional workshops: Argumentation and Society and Argumentation and Philosophy. For the first time, the programme also includes an industry afternoon bringing together businesses, NGOs, academics and students interested in practical applications of argument technologies in industry. The topic of argument mining has substantial representation, both in the accepted papers and demos, and in the invited talks. Dr. Noam Slonim, head of a team at the IBM Haifa Research Lab, presents his team's ground breaking work on debating technologies, and a stalwart of the computational argumentation community – Professor Francesca Toni from Imperial College London – gives an invited talk that traverses the pipeline from argument mining to argumentation semantics. The programme also includes papers reporting on algorithm development, innovative applications, argumentation-based models of dialogue, and abstract argument frameworks whose various types of argument relations reflect the diversity of human uses of argument. A notable recent trend has been the extent to which development of computational models of argument are being informed by the use of argument and proof in mathematical, scientific and philosophical contexts. This is reflected in papers in these proceedings, and in the invited talk given by Marcello D'Agostino, professor of philosophy at the University of Milan. Finally, we point out the presence of papers on structured argumentation, many of which adhere to the Dung paradigm wherein arguments in some formal language are related by conflict based relations in Dung argument frameworks, and variants thereof. It is a testament to the profound and widespread influence of P.M. Dung's work, that his seminal paper On the Acceptability of Arguments and its Fundamental Role in Nonmonotonic Reasoning, Logic Programming and N-person Games, first published in 1995, was awarded the 2018 AIJ Classic Paper Award, which recognizes a paper published at least 15 years ago that has shown to be exceptional in its significance and impact. Indeed, Dung would we believe look favourably on many of the developments reflected in the COMMA'18 programme, and the co-located events in WAW. His paper's dialectical characterisations of non-monotonic inference explicitly aimed at relating nonmonotonic logics to real world reasoning and debate.

We conclude by acknowledging that the success of a conference and its co-located events, depends on the contributions of many people. We would like to thank IOS press for publishing these proceedings and continuing to make them Open Access. We thank the invited speakers, Francesca Toni, Noam Slonim and Marcello D'Agostino for their insightful and inspiring talks. We acknowledge steady support and encouragement by the COMMA Steering Committee, and are very grateful to the Programme Committee and additional reviewers whose invaluable expertise and efforts have led to the selection of 25 full papers and 17 short papers, out of a total of 70 submissions, and 15 demonstration abstracts. The submission and reviewing process has been managed through the Easychair conference system, which we acknowledge for supporting COMMA since the first edition. We would like to express our gratitude for the considerable efforts of the local organizing committee Marcin Koszowy and Maria Załęska, and Brian Plüss for managing the COMMA'18 website. Our thanks also to Barbara Konat and Jakub Zygucki, coordinators of the industry afternoon, the COMMA'18 workshop chairs Matthias Thimm, Katie Atkinson and Jacky Visser, and the summer school chairs Bartłomiej Skowron and Magdalena Kacprzak. Last but not least, we thank all the authors for contributing to the success of the conference with their hard work and commitment.

Sanjay Modgil (Programme chair)

Katarzyna Budzynska (Conference chair)

John Lawrence (Demonstrations chair)

London/Warsaw/Dundee July 2018