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Question 23238: A Depth-Limited No-Hit Is Not an NFA Rejection Proof

On this page
  1. Original question and givens
  2. Definition and scope
  3. Step-by-step derivation
  4. Reverse checks
  5. Result
  6. This question review and source binding

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R0045-23238 · q-20261014-advance-20261111-r07-nondeterministic-finite-automaton-0088

Original question and givens

Use the complete finite epsilon-NFA: states=[s12, m12, f12, d12], alphabet=[a12, b12], start=s12, final_states=[f12], transitions=[[s12, null, m12], [s12, null, d12], [m12, a12, m12], [m12, b12, f12]]. Transitions are [from,input symbol or null,to]; null is epsilon and consumes no input. States are nonempty because the start belongs to them, but alphabet/final sets and the transition relation may be empty. The relation may be multivalued, not deterministic or total. A configuration is [state,input position]; acceptance requires one finite path consuming the entire input and ending final. Input=[b12], max_steps=1. Give (input, max_steps, found_accepting_path, rejection_claim, boundary).

  • G001 — Use the complete finite epsilon-NFA: states=[s12, m12, f12, d12], alphabet=[a12, b12], start=s12, final_states=[f12], transitions=[[s12, null, m12], [s12, null, d12], [m12, a12, m12], [m12, b12, f12]]. Transitions are [from,input symbol or null,to]; null is epsilon and consumes no input. States are nonempty because the start belongs to them, but alphabet/final sets and the transition relation may be empty. The relation may be multivalued, not deterministic or total. A configuration is [state,input position]; acceptance requires one finite path consuming the entire input and ending final. Input=[b12], max_steps=1. Give (input, max_steps, found_accepting_path, rejection_claim, boundary).

Definition and scope

Use the original question domain, assumptions and cited MKO definitions. This item has second-context mathematical and bilingual review, with the model, answer and every arithmetic step independently recomputed from the original parameters; the source question remains a candidate.

Step-by-step derivation

S001 · implies

Before

source operation=nfa-bounded-search-boundary;original snapshot and mathematics retained

After

explicit ordered source output fields=[input, max_steps, found_accepting_path, rejection_claim, boundary]

Conditions: none

Retain the historical interface marker while listing source fields without JavaScript.Tags and No retain their claim scope;source-protocol ordering is not a mathematical proof.

Step identifiers and dependencies

Rule: source_ordered_interface_explicit_without_javascript · Uses: G001

S002 · implies

Before

ORIGINAL transition index=0;[from,input_or_null,to]=[s12, null, m12];state carrier=[s12, m12, f12, d12];alphabet=[a12, b12]

After

state endpoints legal;symbol either declared input or null EPS consuming0;ORIGINAL row position retained,including duplicate rows

Conditions: none

This is a relation,not a total single-valued function.Retain duplicate,multivalued and missing edges;null consumes0 and is not an alphabet string.

Step identifiers and dependencies

Rule: nfa_EVERY_original_relation_row_roles_empty_multi_EPS_legal · Uses: G001, S001

S003 · implies

Before

ORIGINAL transition index=1;[from,input_or_null,to]=[s12, null, d12];state carrier=[s12, m12, f12, d12];alphabet=[a12, b12]

After

state endpoints legal;symbol either declared input or null EPS consuming0;ORIGINAL row position retained,including duplicate rows

Conditions: none

This is a relation,not a total single-valued function.Retain duplicate,multivalued and missing edges;null consumes0 and is not an alphabet string.

Step identifiers and dependencies

Rule: nfa_EVERY_original_relation_row_roles_empty_multi_EPS_legal · Uses: G001, S002

S004 · implies

Before

ORIGINAL transition index=2;[from,input_or_null,to]=[m12, a12, m12];state carrier=[s12, m12, f12, d12];alphabet=[a12, b12]

After

state endpoints legal;symbol either declared input or null EPS consuming0;ORIGINAL row position retained,including duplicate rows

Conditions: none

This is a relation,not a total single-valued function.Retain duplicate,multivalued and missing edges;null consumes0 and is not an alphabet string.

Step identifiers and dependencies

Rule: nfa_EVERY_original_relation_row_roles_empty_multi_EPS_legal · Uses: G001, S003

S005 · implies

Before

ORIGINAL transition index=3;[from,input_or_null,to]=[m12, b12, f12];state carrier=[s12, m12, f12, d12];alphabet=[a12, b12]

After

state endpoints legal;symbol either declared input or null EPS consuming0;ORIGINAL row position retained,including duplicate rows

Conditions: none

This is a relation,not a total single-valued function.Retain duplicate,multivalued and missing edges;null consumes0 and is not an alphabet string.

Step identifiers and dependencies

Rule: nfa_EVERY_original_relation_row_roles_empty_multi_EPS_legal · Uses: G001, S004

S006 · implies

Before

ORIGINAL states=[s12, m12, f12, d12],alphabet=[a12, b12],start=s12,final_states=[f12];complete relation=[[s12, null, m12], [s12, null, d12], [m12, a12, m12], [m12, b12, f12]]

After

states nonempty with actual start;alphabet/final set/relation MAY be EMPTY;definition qualification does NOT prove determinism,totality,DFA equivalence or a successful run

Conditions: none

An empty final set is legal and recognizes the empty language;an empty alphabet is legal too.A qualified definition supplies no accepting path,determinism or DFA-equivalence proof.

Step identifiers and dependencies

Rule: nfa_qualified_definition_EMPTY_alphabet_finals_edges_allowed · Uses: G001, S005

S007 · implies

Before

ORIGINAL input=[b12];actual start configuration=[s12, 0];max_steps=1

After

depth0 accepted=No;one finite FULL-input final path suffices;dead alternatives do not veto success

Conditions: none

The bound counts transitions:an EPS move still costs a step despite consuming no input.An initially final start accepts empty input.One finite full-input final path suffices;not all branches must succeed.

Step identifiers and dependencies

Rule: nfa_bounded_initial_and_finite_path_acceptance_scope · Uses: G001, S006

S008 · implies

Before

ORIGINAL depth=0;frontier in ORIGINAL-state/position display order=[[s12, 0]]

After

ALL [from,ORIGINAL transition index,next_or_null] rows=[[[s12, 0], 0, [m12, 0]], [[s12, 0], 1, [d12, 0]], [[s12, 0], 2, null], [[s12, 0], 3, null]];next distinct configs=[[m12, 0], [d12, 0]];hit FULL-input final=No

Conditions: none

Check every configuration and original relation row,with per-depth deduplication.Input position increases1 or0 according to symbol or null.An EPS cycle permits paths but is not an infinite accepting run.

Step identifiers and dependencies

Rule: nfa_ALL_nondeterministic_bounded_frontier_not_infinite_cycle · Uses: G001, S007

S009 · implies

Before

ORIGINAL bound=1;input=[b12];found_accepting_path=No

After

rejection_claim fixed No;bounded flag alone supplies no GENERAL rejection certificate;any actual completeness argument must be established separately

Conditions: none

The final No withholds a general rejection inference from finite tests,without negating found=True.If a finite model separately proves this bound complete,actual rejection may be decided;do not substitute that different completeness claim for this found flag.

Step identifiers and dependencies

Rule: nfa_bounded_No_rejection_claim_not_found_negation · Uses: G001, S008

Reverse checks

  • S009 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S008 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S007 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S006 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S005 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S004 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S003 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S002 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S001 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.

Result

([b12], 1, No, No, bounded_search_failure_cannot_prove_rejection_and_epsilon_cycles_are_not_infinite_accepting_runs)

The full substitutions and premise checks give the original answer; source identity,format and status are unchanged.

This question review and source binding

Review date: 2026-10-26

Original questions, answers, step expressions, numeric ASTs and historical records are retained. Source candidate labels remain historical and are not overwritten as formal proof.

Source hashes and review receipts
  • input commit: 0f7be61e2c22317a4075561dc822c87d881a50db
  • original question SHA-256: 59968f9b09568215f917ed7c0edb72da3bfac0b81e896506ee1dc74149fdaaf8
  • candidate record SHA-256: f01be82cb8457bd9ce1dec188058991f0b1b2b2a26d9457545ebdf2fd711a0eb
  • semantic review receipt SHA-256: 357d7ad7a6726b2a757558d3b9586a408ade06526cc023da093719c292704438
  • question-first witness SHA-256: 99cefe17e98c7a74321801cf72df6d02fc95b6a6b78aa335accb7e11ed467b2a
  • Lean: NOT_RUN · human review: NOT_PERFORMED
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