A Hierarchy of SOS Rule Formats (Preliminary abstract)

In 1981 Structural Operational Semantics (SOS) was introduced as a systematic way to define operational semantics of programming languages by a set of rules of a certain shape [56]. Subsequently, the rule format became object of study. Using so-called Transition System Specifications (TSSs) several authors syntactically restricted the format of rules and showed several useful properties about the semantics induced by any TSS adhering to the format. This has resulted in a line of research proposing several syntactical rule formats and associated meta-theorems. Properties that are guaranteed by such rule formats range from well-definedness of the operational semantics and compositionality of behavioral equivalences to securityand probability-related issues. In this paper, we provide an initial hierarchy of SOS rules formats and meta-theorems formulated around them