Distributive Laws and Decidable Properties of SOS Specifications

Some formats of well-behaved operational specifications, correspond to natural transformations of certain types (for example, GSOS and coGSOS laws). These transformations have a common generalization: distributive laws of monads over comonads. We prove that this elegant theoretical generalization has limited practical benefits: it does not translate to any concrete rule format that would be complete for specifications that contain both GSOS and coGSOS rules. This is shown for the case of labeled transition systems and deterministic stream systems.Comment: In Proceedings EXPRESS/SOS 2014, arXiv:1408.127

Distributive Laws for Monotone Specifications

Turi and Plotkin introduced an elegant approach to structural operational semantics based on universal coalgebra, parametric in the type of syntax and the type of behaviour. Their framework includes abstract GSOS, a categorical generalisation of the classical GSOS rule format, as well as its categorical dual, coGSOS. Both formats are well behaved, in the sense that each specification has a unique model on which behavioural equivalence is a congruence. Unfortunately, the combination of the two formats does not feature these desirable properties. We show that monotone specifications - that disallow negative premises - do induce a canonical distributive law of a monad over a comonad, and therefore a unique, compositional interpretation.Comment: In Proceedings EXPRESS/SOS 2017, arXiv:1709.0004

The Way We Were: Structural Operational Semantics Research in Perspective

This position paper on the (meta-)theory of Structural Operational Semantic (SOS) is motivated by the following two questions: (1) Is the (meta-)theory of SOS dying out as a research field? (2) If so, is it possible to rejuvenate this field with a redefined purpose? In this article, we will consider possible answers to those questions by first analysing the history of the EXPRESS/SOS workshops and the data concerning the authors and the presentations featured in the editions of those workshops as well as their subject matters. The results of our quantitative and qualitative analyses all indicate a diminishing interest in the theory of SOS as a field of research. Even though `all good things must come to an end', we strive to finish this position paper on an upbeat note by addressing our second motivating question with some optimism. To this end, we use our personal reflections and an analysis of recent trends in two of the flagship conferences in the field of Programming Languages (namely POPL and PDLI) to draw some conclusions on possible future directions that may rejuvenate research on the (meta-)theory of SOS. We hope that our musings will entice members of the research community to breathe new life into a field of research that has been kind to three of the authors of this article.Comment: In Proceedings EXPRESS/SOS2023, arXiv:2309.0578

On Extensibility of Software Systems

This report contains the progress report written as part of the author's PhD qualifying exam. It describes initial work carried out in analyzing and improving the extensibility of software systems, including a detailed case study analyzing the extensibility of the Proof Obligation Generator (POG) of the Overture tool. Additional extension work includes improving the output format of the POG and support for additional logic systems. Future work for the remaining half of the PhD is also discussed, including ways to combine formal modelling and extensibility analysis and also techniques for multi-paradigm extensibility

Asserting the Correctness of Software Language Translations

While building a new language, we assign its semantics by mapping its syntax onto a semantic domain. To do so, we can either (i) do it operationally, by means of small-step morphisms within the same semantic-domain; or (ii) by means of a translation (syntax-to-syntax transformation), onto a target language that has already an operational semantics defined. Despite the fact that it is possible to build the set of syntactic correspondences from a given translation, it is still not clear how we can assert about the correctness of these syntactic correspondences in w.r.t. both the source and target language's underlying semantics.In this paper, we combine the above described techniques by analyzing the translation and establishing a semantic relation between the respective operational semantics, in order to assert the correctness of that translation. We demonstrate our approach with a concrete translation between two languages: State Machines and Petri Nets; and decide about its correctness by using their respective operational semantics as oracles. Finally, we discuss about the validity of our assertions in w.r.t. language translations in general