Congratulations to all the authors for inclusion in this special issue, most notably those from the SERC Research network.

- Employing SysML to model and explore levels-of-service: The case of passenger comfort in railway transportation systems
Christos Kotronis, Mara Nikolaidou, George-Dimitrios Kapos, Anargyros Tsadimas, Vassilis Dalakas, Dimosthenis Anagnostopoulos
First Published: 29 August 2019 - Handling the COVID-19 crisis: Toward an agile model-based systems approach
Olivier de Weck, Daniel Krob, Li Lefei, Pao Chuen Lui, Antoine Rauzy, Xinguo Zhang
First Published: 27 August 2020 - Set-based design: The state-of-practice and research opportunities
Nicholas Shallcross, Gregory S. Parnell, Ed Pohl, Eric Specking
First Published: 03 July 2020 - System-of-systems tools and techniques for the analysis of cyber-physical systems
Cesare Guariniello, Ali Khalid Raz, Zhemei Fang, Daniel DeLaurentis
First Published: 28 May 2020 - Systems modeling language extension to support modeling of human-agent teams
Michael E. Miller, John M. McGuirl, Michael F. Schneider, Thomas C. Ford
First Published: 02 June 2020