The citation for the award is available from the above-mentioned web page, but I repeat it here for ease of reference:
Session types are a type-based framework for codifying communication structures and verifying protocols in concurrent, message-passing programs. Previously, session types could only model binary (two-party) protocols. This paper generalizes the theory to the multiparty case with asynchronous communications, preventing deadlock and communication errors in more sophisticated communication protocols involving any number (two or more) of participants. The central idea was to introduce global types, which describe multiparty conversations from a global perspective and provide a means to check protocol compliance. This work has inspired numerous authors to build on its pioneering foundations in the session types community and has initiated many applications of multiparty session types in programming languages and tools. It has also influenced other areas of research, such as software contracts, runtime verification and hardware specifications.
Congratulations to the authors of the paper and to the concurrency community at large, whose work over the last ten years contributed to this award and, most importantly, to significant scientific advances that are now embodied in programming languages and tools that are already having practical impact (see the work with Cognizant, Red Hat, and VMWare on Scribble, and with the OOI), and that I believe will find increasing application in years to come.