RumbleDB is an open-source query engine for processing large, heterogeneous datasets using the declarative languages JSONiq and XQuery. At the previous Declarative Amsterdam, RumbleDB introduced its initial support for XQuery 3.1, bringing XML processing alongside JSON to its local and distributed execution engine.

In this presentation, I will present the results of my Master’s thesis, whose goal is to bring RumbleDB to full XQuery 3.1 support. This involves implementing missing language features, including tumbling and sliding windows, as well as adding XML Schema support. In parallel, Henrik has been extending RumbleDB’s coverage of XQuery built-in functions. Progress is systematically validated against the official QT3 test suite. At the time of submission, RumbleDB passes 90.3% of the test suite, with some additional cases intentionally skipped, and the thesis aims to reach full coverage by its completion.

In parallel, I developed a new language server for both JSONiq and XQuery, together with a Visual Studio Code extension, to provide a modern development experience for these languages. It supports features like document formatting, query execution directly from the editor, module-aware analysis, and inline completion. It also exposes RumbleDB’s type information through hover, allowing developers to inspect the inferred type of an expression directly in their source code.

Together, these contributions aim to make RumbleDB both a comprehensive implementation of XQuery 3.1 and a practical, modern development environment for declarative querying over heterogeneous data.