Preface

The 16th International Conference on Automata and Formal Languages (AFL 2023) was held in Eger, September 5-7, 2023. It was organized by the Eszterházy Károly Catholic University of Eger, Hungary, and the University of Szeged, Hungary. Topics of interest covered the theory and applications of automata and formal languages and related areas.

The scientific program consisted of invited lectures by

• Galina Jírásková (Slovak Academy of Sciences, Košice),
• Andreas Maletti (Universität Leipzig),
• Victor Mitrana (Polytechnic University of Madrid and National Institute of R&D for Biological Sciences, Bucharest),

This volume contains the texts of the invited presentations and the 18 papers selected by the International Program Committee from a total of 23 submissions. We would like to thank everybody who submitted a paper to the conference. We are especially grateful to the invited speakers for presenting interesting new developments.

The members of the International Program Committee were

• Francine Blanchet-Sadri (UNC Greensboro),
• Henning Bordihn (Universität Potsdam),
• Miroslav Ćirić (University of Niš),
• Erzsébet Csuhaj-Varjú (Eötvös Loránd University, Budapest),
• Pál Dömösi (University of Nyíregyháza),
• Gabriele Fici (Università di Palermo),
• Zoltán Fülöp (University of Szeged),
• Zsolt Gazdag (University of Szeged, co-chair),
• Viliam Geffert (P. J. Šafárik University, Košice),
• Géza Horváth (University of Debrecen),
• Szabolcs Iván (University of Szeged, co-chair),
• Roland Király (Eszterházy Károly Catholic University, Eger),
• Gergely Kovásznai (Eszterházy Károly Catholic University, Eger, head of the local organizing committee),
• Martin Kutrib (Universität Gießen),
• Andreas Malcher (Universität Gießen),
• František Mráz (Charles University, Prague),
• Benedek Nagy (Eastern Mediterranean University, Famagusta; Eszterházy Károly Catholic University, Eger),
• Chrystopher L. Nehaniv (University of Waterloo),
• Giovanni Pighizzini (University of Milan),
• Agustín Riscos-Nunez (Universidad de Sevilla),
• Kai Salomaa (Queen's University, Kingston),
• Petr Sosík (Silesian University in Opava),
• Bianca Truthe (Universität Gießen),
• György Vaszil (University of Debrecen).

The members of the Steering Committee overseeing the AFL series are

• András Ádám (Budapest, honorary chair),
• István Babcsányi (Budapest),
• Erzsébet Csuhaj-Varjú (Budapest),
• Pál Dömösi (Nyíregyháza, chair),
• Zoltán Fülöp (Szeged),
• Zsolt Gazdag (Szeged),
• Géza Horváth (Debrecen),
• László Hunyadvári (Budapest),
• Szabolcs Iván (Szeged),
• László Kászonyi (Szombathely),
• Gergely Kovásznai (Eger),
• Attila Nagy (Budapest),
• György Vaszil (Debrecen).

We thank all members of the Program Committee and their subreferees for their excellent cooperation in the selection of the papers. We are grateful to the Faculty of Informatics of the Eszterházy Károly Catholic University of Eger and the Institute of Informatics of University of Szeged for the local organization and financial support of AFL 2023.

Eger, September 2023.

Zsolt Gazdag, Szabolcs Iván, and Gergely Kovásznai

Compositions of Weighted Extended Top-Down Tree Transducers

Weighted extended top-down tree transducers are a natural generalization of the classic top-down tree transducers, but their compositions pose additional problems due to the extension as well as the weights. We review the basic composition results of [1] of the unweighted case and the basic composition approach of [2] or the weighted case. Additionally we report on recent progress on the conjectures raised in the latter reference. In particular we recently were able to obtain results that mirror the classical composition results for top-down tree transducers.

References

1. Joost Engelfriet, Zoltán Fülöp & Andreas Maletti (2017): Composition closure of linear extended top-down tree transducers. Theory of Computing Systems 60(2), pp. 129–171, doi:10.1007/s00224-015-9660-2.
2. Aurélie Lagoutte & Andreas Maletti (2011): Survey: Weighted Extended Top-Down Tree Transducers Part III – Composition. In: Algebraic Foundations in Computer Science, Lecture Notes in Computer Science 7020, pp. 272–308, doi:10.1007/978-3-642-24897-9_13.