Recovering Grammar Relationships for the Java Language Specification

TL;DR

This paper introduces a refined grammar convergence method that automates the analysis of relationships between different versions of the Java Language Specification grammars, providing detailed transformation chains and insights.

Contribution

It presents a new, mechanized approach for grammar convergence, specifically applied to recover relationships among all JLS grammar versions, with detailed transformation operators and metadata.

Findings

Recovered relationships between all JLS grammar versions

Automated transformation chains capturing grammar differences

Enhanced transparency and reproducibility of the convergence process

Abstract

Grammar convergence is a method that helps discovering relationships between different grammars of the same language or different language versions. The key element of the method is the operational, transformation-based representation of those relationships. Given input grammars for convergence, they are transformed until they are structurally equal. The transformations are composed from primitive operators; properties of these operators and the composed chains provide quantitative and qualitative insight into the relationships between the grammars at hand. We describe a refined method for grammar convergence, and we use it in a major study, where we recover the relationships between all the grammars that occur in the different versions of the Java Language Specification (JLS). The relationships are represented as grammar transformation chains that capture all accidental or intended differences between the JLS grammars. This method is mechanized and driven by nominal and structural differences between pairs of grammars that are subject to asymmetric, binary convergence steps. We present the underlying operator suite for grammar transformation in detail, and we illustrate the suite with many examples of transformations on the JLS grammars. We also describe the extraction effort, which was needed to make the JLS grammars amenable to automated processing. We include substantial metadata about the convergence process for the JLS so that the effort becomes reproducible and transparent.