"book-pflow-xyz/chapters/appendix-d-glossary.md" . . "The tense structure of an executing model. Write-once places and the event log are the *past* — monotone and irreversible, the boolean case of tropical $(\\max,+)$ accumulation. Guards are the *future* — predicates recomputed from the marking on every step and stored nowhere. The marking is the *present*, the boundary where they meet. All three are data in the one model document (Chapter 6; Appendix E; *The Zipper Whose Hole Is a Universe*)."@en . . "Tropical past, predicate future"@en . "6"^^ .