­Best Paper Award for Michael Sippel and Horst Schirmeier

Michael Sippel and Horst Schirmeier (Chair of Operating Systems) won the Best Paper Award for their publication on "Process Composition with Typed Unix Pipes" at the renowned Workshop on Programming Languages and Operating Systems (PLOS) as part of the Symposium on Operating Systems Principles (SOSP) in October. The publication is based on a thesis by Mr. Sippel. The PLOS workshop is well-recognized in the systems community and discusses topics at the interface between operating systems and (programming) languages.

The paper deals with a basic communication mechanism, the so-called pipe, which realizes a unidirectional data stream between processes and has found its way into all common desktop and mobile operating systems since its inception for Unix. Pipes can be used to combine simple, small programs to solve complex problems – a common practice in Unix-like systems such as Linux or macOS when working on the command line or in shell scripts.

However, the operating system has no information about what kind of data flows through a pipe from one process to another – be it integer numbers, calendar data or file names, for example. This entails the danger of inadvertently combine programs whose output and input data are incompatible, leading to error messages or, in the worst case, data loss.

With "Ladder Types", the paper proposes a type system for pipes that can be used to detect such errors and diagnose them in detail for the user. Ladder types combine an abstract data type with several possible forms of representation and thereby – in contrast to previous work – maintain compatibility with the existing Unix tool ecosystem. The paper also describes a prototype implementation and its effectiveness using several example pipes.