Waiting Nets: State Classes and Taxonomy
Pith reviewed 2026-05-24 11:09 UTC · model grok-4.3
The pith
Bounded waiting nets admit a finite state class graph that decides reachability and coverability while generating strictly more timed languages than time Petri nets.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Waiting nets decouple time measurement from full transition enabling and relax urgency when resources remain unavailable. For bounded instances the paper constructs a finite state class graph by tracking sets of enabled transitions together with symbolic time intervals that account for the waiting semantics. Inspection of this graph decides reachability and coverability. With respect to timed language equivalence the class of waiting nets strictly contains the class of time Petri nets.
What carries the argument
Finite state class graph obtained by symbolic abstraction of control states and time intervals under the waiting semantics that allow partial presets and delayed firing after upper bounds.
If this is right
- Reachability is decidable for every bounded waiting net.
- Coverability is decidable for every bounded waiting net.
- Waiting nets can generate timed languages outside the expressive power of time Petri nets.
- The finite-graph construction remains valid even though urgency is relaxed and time may start on incomplete presets.
Where Pith is reading between the lines
- The waiting semantics may capture systems in which timers run independently of resource acquisition without immediately losing decidability.
- Waiting nets occupy an intermediate position between time Petri nets and stopwatch extensions that are already known to be undecidable on bounded nets.
- The expressiveness gap suggests that any complete taxonomy of timed Petri-net variants must place waiting nets strictly above ordinary time Petri nets.
Load-bearing premise
The waiting nets under consideration are bounded, that is, each place can hold only finitely many tokens.
What would settle it
A concrete bounded waiting net whose successive state classes keep producing new time intervals indefinitely, or a timed word accepted by some waiting net but rejected by every time Petri net.
Figures
read the original abstract
In time Petri nets (TPNs), time and control are tightly connected: time measurement for a transition starts only when all resources needed to fire it are available. Further, upper bounds on duration of enabledness can force transitions to fire (this is called urgency). For many systems, one wants to decouple control and time, i.e. start measuring time as soon as a part of the preset of a transition is filled, and fire it after some delay \underline{and} when all needed resources are available. This paper considers an extension of TPN called waiting nets that dissociates time measurement and control. Their semantics allows time measurement to start with incomplete presets, and can ignore urgency when upper bounds of intervals are reached but all resources needed to fire are not yet available. Firing of a transition is then allowed as soon as missing resources are available. It is known that extending bounded TPNs with stopwatches leads to undecidability. Our extension is weaker, and we show how to compute a finite state class graph for bounded waiting nets, yielding decidability of reachability and coverability. We then compare expressiveness of waiting nets with that of other models w.r.t. timed language equivalence, and show that they are strictly more expressive than TPNs.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper claims that waiting nets, an extension of time Petri nets allowing time measurement to start with incomplete presets and ignoring urgency in certain cases, admit a finite state class graph when bounded, leading to decidability of reachability and coverability. It also claims strict expressiveness superiority over TPNs w.r.t. timed language equivalence.
Significance. If substantiated, the results would offer a decidable yet more expressive alternative to TPNs for modeling timed systems, positioned between TPNs and undecidable stopwatch TPNs. The state class graph would enable practical verification.
major comments (1)
- [Abstract] The finite state class graph construction for bounded waiting nets and the proof of strict timed-language expressiveness over TPNs are asserted without any construction details, proof sketches, or counter-examples provided in the visible text. These are load-bearing for the central claims of decidability and the taxonomy.
Simulated Author's Rebuttal
We thank the referee for their review. The major comment concerns the level of detail in the abstract; we clarify that the full manuscript contains the requested constructions and proofs, as summarized below.
read point-by-point responses
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Referee: [Abstract] The finite state class graph construction for bounded waiting nets and the proof of strict timed-language expressiveness over TPNs are asserted without any construction details, proof sketches, or counter-examples provided in the visible text. These are load-bearing for the central claims of decidability and the taxonomy.
Authors: The abstract is a high-level summary; the finite state class graph construction (including the algorithm for computing classes and the proof that it remains finite for bounded waiting nets) is given in full in Section 3, with the decidability corollaries following directly. The strict expressiveness result over TPNs (via timed language equivalence) is established in Section 4 by exhibiting a concrete timed language accepted by a waiting net but not by any TPN, together with the formal proof. We can add one-sentence pointers to these sections in a revised abstract if the editor prefers. revision: partial
Circularity Check
No significant circularity
full rationale
The paper defines waiting nets via new semantics that decouple time measurement from control, then constructs a finite state class graph explicitly for the bounded case. Decidability of reachability/coverability follows as a direct consequence of that construction. The strict expressiveness claim over TPNs is obtained by exhibiting timed languages that waiting nets can realize but TPNs cannot. No equations reduce a claimed result to a fitted parameter or to a self-citation chain; the central arguments rest on the freshly stated operational rules and the standard state-class technique adapted to the new firing condition. The known undecidability of stopwatch extensions is invoked only as contrast and is not load-bearing for the positive results.
Axiom & Free-Parameter Ledger
axioms (1)
- domain assumption The waiting net is bounded
invented entities (1)
-
Waiting net
no independent evidence
Lean theorems connected to this paper
-
IndisputableMonolith/Foundation/RealityFromDistinction.leanreality_from_one_distinction unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
We show how to compute a finite state class graph for bounded waiting nets, yielding decidability of reachability and coverability... state class graphs of waiting nets are not deterministic
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IndisputableMonolith/Cost/FunctionalEquation.leanwashburn_uniqueness_aczel unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
Domains... ai ≤ θi ≤ bi ... θj − θk ≤ cjk ... canonical form via Floyd-Warshall
What do these tags mean?
- matches
- The paper's claim is directly supported by a theorem in the formal canon.
- supports
- The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
- extends
- The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
- uses
- The paper appears to rely on the theorem as machinery.
- contradicts
- The paper's claim conflicts with a theorem or certificate in the canon.
- unclear
- Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.
Reference graph
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where v′ 0(t) = v0(t) + d1 if t ∈ FullyEnabled(M0. N0), v′ 0(t) = min( v(t) + d1, β (t)) if t ∈ enabled(M0) \ FullyEnabled(M0) and v′ 0(t) = ⊥ otherwise. The valuation v1 is computed according to timed moves rules, which means that v1(t) = 0 if t ∈↑ enabled(M1, t 1) , v ′ 0(t) if t ∈ Enabled(M0) ∩ Enabled(M1) ⊥ otherwise Now, since ρ = ( M0.N 0,...
discussion (0)
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