CoCon will develop Longitudinal Institutional Grammar (L-IG) by combining Common Rules, which codes what historical rules regulate (De Moor et al., 2016). with Institutional Grammar 2.0, which decomposes institutional statements into actors, actions, deontic functions, conditions, objects and sanctions (Bunders & De Moor, 2024; Crawford & Ostrom, 1995). LLM-assisted decomposition will support scale (Groep-Foncke & De Moor, 2025), while a new longitudinal layer links successive rule variants and models persistence, modification and recombination. For example, a historical common may condition resource access on membership and collectively determined quotas. A later cooperative may retain membership-based access while transferring quota-setting from the members’ assembly to an elected board, while a contemporary collective may recombine membership-based access with assembly decision-making and ecological conditions. L-IG decomposes these rules into comparable grammatical and substantive components and links successive variants, allowing persistence, modification and recombination to be distinguished from superficial similarity.

L-IG converts static rules into candidate evolutionary trajectories. Links are not treated as descent merely because rules resemble one another: continuity in content and grammar must also be chronologically and historically plausible, and confidence remains explicit. Groups of interacting rule genealogies reveal how institutional repertoires are assembled, disassembled and recombined across organisations and periods. Candidate genealogies therefore remain hypotheses of descent until the other inferential layers test whether transmission is more plausible than independent convergence. This genealogical logic, familiar from language and cultural transmission (Gray & Atkinson, 2003; Mesoudi, 2011; Pagel, 2009) is applied to institutional rules while retaining historical source criticism and uncertainty. It creates the analytical instrument needed to make institutional inheritance empirically testable.