Invited Articles Foreword

The Invited Article section of this issue consists of two papers. The first is “Complexity Analysis of Generalized and Fractional Hypertree Decompositions” by Georg Gottlob, Matthias Lanzinger, Reinhard Pichler, and Igor Razgon, that was invited from the 37th ACM SIGMOD-SIGACT-SIGAI Symposium on Principles of Database Systems (PODS 2018). We want to thank the PODS’18 Program Committee for their help in selecting this invited paper, and editor Dan Suciu for handling the paper. The second is “Lower Bounds for Maximal Matchings and Maximal Independent Sets” by Alkida Balliu, Sebastian Brandt, Juho Hirvonen, Dennis Olivetti, Mikaël Rabie, and Jukka Suomela, which won the best paper award at the 60th Annual IEEE Symposium on Foundations of Computer Science (FOCS 2019). We want to thank the FOCS’19 Program Committee for their help in selecting this invited paper, and editor Rachit Guerraoui for handling the paper.