Acknowledgements

This book stands on German work that is older than the phrase “law as code”. Gottfried Wilhelm Leibniz, a doctor of law before he was known as a mathematician, argued in 1667 in his Nova methodus discendae docendaeque jurisprudentiae that jurisprudence could be taught as a method. The Bürgerliches Gesetzbuch, in force since 1 January 1900, gave the world a general part and a systematic order that many codes still follow. Wilhelm Steinmüller’s EDV und Recht (1970) and Herbert Fiedler’s work in Bonn helped open the field of Rechtsinformatik; Hesse passed the world’s first data-protection act the same year. Since 1985 juris has kept German law searchable; gesetze-im-internet.de made federal law free to read, and DigitalService is building NeuRIS, a new public portal for legal information.

Today’s work continues that line. GETTSIM models German taxes and transfers in the open. The Digitalcheck asks every federal bill whether it can be executed digitally. And Catala — the pioneer of statute-as-code from Inria — showed that a statute can be written as code beside its own text.

This book follows an independent Arxo model built from published texts. Where it compares tools, it names the version and the date of the check (Appendix F).

Sources

• Wohngeldgesetz (WoGG) and Wohngeldverordnung (WoGV) — consolidated texts from gesetze-im-internet.de, provided by the Federal Ministry of Justice; German statutes and ordinances are free of copyright under § 5 UrhG.
• Bundesgesetzblatt — BGBl. 2024 I Nr. 314 (second WoGFV) and BGBl. 2026 I Nr. 107 from recht.bund.de; BGBl. I 2021 S. 1369 and BGBl. I 2022 S. 2160 from the copies published by OffeneGesetze.de.
• Einkommensteuergesetz (EStG) — § 2 and § 9a, for the definition of income the WoGG refers to.
• Federal Ministry for Housing, Urban Development and Building (BMWSB) — Rechenbeispiele 2023 and Beispiele für die Berechnung des Wohngelds, as of 1 January 2025. Their worked examples are the expectations of the model’s scenarios; the book reuses their facts and numbers, not their text.
• German Bundestag — BT-Drs. 21/8284 of 30 September 2026, the government bill for 2027, cited for its status only.

If something in this book is wrong or out of date, tell us at hi@arxo.io and we will correct it.