# Question 10793: A Two-Time Joint Distribution Keeps the Requested Time Order [Return to catalogue page 54](https://ocme.evemisslab.com/en/questions/page/54/) [← Question derivation index](https://ocme.evemisslab.com/en/questions/) · [Original question batch](https://ocme.evemisslab.com/en/practice/batch-20261013-advance-20261023-r06-discrete-stochastic-process-foundations/#q-20261013-advance-20261023-r06-discrete-stochastic-process-0093) This teaching derivation has second-context AI mathematical and bilingual semantic review, limited to the model and assumptions stated in this question. It has no human review or new Lean proof and does not promote the original question or MKO to Canonical truth. R0020-10793 · q-20261013-advance-20261023-r06-discrete-stochastic-process-0093 ## Original question and givens Use one common finite probability space specified by the complete distinct equal-horizon path list=[[17, 17, 18], [17, 18, 18], [18, 18, 17]] and aligned exact masses=[1/4, 1/4, 1/2]. Preserve the original path-mass pairing. A qualified joint path law has nonnegative masses summing exactly to 1. Time starts at 0. Marginals do not determine the joint law or Markov property; a finite horizon gives no stationarity, ergodicity or infinite-time extension. Use exact reduced rational outputs with positive denominators, omitting /1 for integers. Require a qualified law. time_a=2, time_b=0. Give (time_a,time_b,every [[state at time_a,state at time_b],aggregated mass] row). Order distinct output pairs by the source’s en-locale comparison of their JSON strings, not numeric coordinate sorting. Equal requested times are allowed. - G001 — Use one common finite probability space specified by the complete distinct equal-horizon path list=[[17, 17, 18], [17, 18, 18], [18, 18, 17]] and aligned exact masses=[1/4, 1/4, 1/2]. Preserve the original path-mass pairing. A qualified joint path law has nonnegative masses summing exactly to 1. Time starts at 0. Marginals do not determine the joint law or Markov property; a finite horizon gives no stationarity, ergodicity or infinite-time extension. Use exact reduced rational outputs with positive denominators, omitting /1 for integers. Require a qualified law. time_a=2, time_b=0. Give (time_a,time_b,every [[state at time_a,state at time_b],aggregated mass] row). Order distinct output pairs by the source’s en-locale comparison of their JSON strings, not numeric coordinate sorting. Equal requested times are allowed. ## 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. - [mko-discrete-stochastic-process](https://ocme.evemisslab.com/en/mko/mko-discrete-stochastic-process/) ## Step-by-step derivation S001 · impliesBefore original support index=0;path=[17, 17, 18];raw mass=[1, 4] After aligned reduced mass=1/4 Conditions: none Complete paths are distinct and share one positive horizon.Masses remain paired to original support indices.Reduce fractions only:do not sort paths or divide by a total to repair an unqualified candidate. Step identifiers and dependenciesRule: path_mass_original_support_pairing · Uses: G001 S002 · impliesBefore original support index=1;path=[17, 18, 18];raw mass=[1, 4] After aligned reduced mass=1/4 Conditions: none Complete paths are distinct and share one positive horizon.Masses remain paired to original support indices.Reduce fractions only:do not sort paths or divide by a total to repair an unqualified candidate. Step identifiers and dependenciesRule: path_mass_original_support_pairing · Uses: G001, S001 S003 · impliesBefore original support index=2;path=[18, 18, 17];raw mass=[1, 2] After aligned reduced mass=1/2 Conditions: none Complete paths are distinct and share one positive horizon.Masses remain paired to original support indices.Reduce fractions only:do not sort paths or divide by a total to repair an unqualified candidate. Step identifiers and dependenciesRule: path_mass_original_support_pairing · Uses: G001, S002 S004 · calculationBefore whole path-law mass sum := sum(1/4, 1/4, 1/2) After whole path-law mass sum = 1 Conditions: none Compute exactly with this step's original roles and operands,without floating approximation or reordering source data. Step identifiers and dependenciesRule: exact_rational_arithmetic · Uses: G001, S003 S005 · impliesBefore horizon=3;normalized aligned masses=[1/4, 1/4, 1/2] After all nonnegative=Yes;total=1;qualified joint law=Yes Conditions: none The qualification task may retain negative or unnormalized masses to report failure.Marginal/event/joint queries require the whole law nonnegative with total exactly1.A finite horizon establishes neither Markov behavior nor stationarity. Step identifiers and dependenciesRule: whole_finite_joint_law_qualification · Uses: G001, S004 S006 · calculationBefore joint path0 bucket update := sum(0, 1/4) After joint path0 bucket update = 1/4 Conditions: none Compute exactly with this step's original roles and operands,without floating approximation or reordering source data. Step identifiers and dependenciesRule: exact_rational_arithmetic · Uses: G001, S005 S007 · impliesBefore support index=0;ordered times=[2, 0];ordered state pair=[18, 17];original mass=1/4;previous bucket=0 After updated pair mass=1/4 Conditions: none Keep time_a first and time_b second;equal times are allowed.Do not replace path-based joint mass by a product of marginals. Step identifiers and dependenciesRule: joint_original_time_order_and_mass_pairing · Uses: G001, S006 S008 · calculationBefore joint path1 bucket update := sum(1/4, 1/4) After joint path1 bucket update = 1/2 Conditions: none Compute exactly with this step's original roles and operands,without floating approximation or reordering source data. Step identifiers and dependenciesRule: exact_rational_arithmetic · Uses: G001, S007 S009 · impliesBefore support index=1;ordered times=[2, 0];ordered state pair=[18, 17];original mass=1/4;previous bucket=1/4 After updated pair mass=1/2 Conditions: none Keep time_a first and time_b second;equal times are allowed.Do not replace path-based joint mass by a product of marginals. Step identifiers and dependenciesRule: joint_original_time_order_and_mass_pairing · Uses: G001, S008 S010 · calculationBefore joint path2 bucket update := sum(0, 1/2) After joint path2 bucket update = 1/2 Conditions: none Compute exactly with this step's original roles and operands,without floating approximation or reordering source data. Step identifiers and dependenciesRule: exact_rational_arithmetic · Uses: G001, S009 S011 · impliesBefore support index=2;ordered times=[2, 0];ordered state pair=[17, 18];original mass=1/2;previous bucket=0 After updated pair mass=1/2 Conditions: none Keep time_a first and time_b second;equal times are allowed.Do not replace path-based joint mass by a product of marginals. Step identifiers and dependenciesRule: joint_original_time_order_and_mass_pairing · Uses: G001, S010 S012 · impliesBefore ordered times=[2, 0];distinct JSON pair keys=["[18,17]","[17,18]"] After en-locale JSON-string ordered joint rows=[[[17, 18], 1/2], [[18, 17], 1/2]] Conditions: none Order by English-locale comparison of each pair's JSON string,not numeric coordinate order.This orders presentation only,without changing a pair or its mass. Step identifiers and dependenciesRule: joint_pair_source_locale_order · Uses: G001, S011 ## Reverse checks - S012 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence. - S011 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence. - S010 · premise_and_result_audit — Recompute joint path2 bucket update with exact rational arithmetic, not rounded decimals. - 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 — Recompute joint path1 bucket update with exact rational arithmetic, not rounded decimals. - 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 — Recompute joint path0 bucket update with exact rational arithmetic, not rounded decimals. - 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 — Recompute whole path-law mass sum with exact rational arithmetic, not rounded decimals. - 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 (2, 0, [[[17, 18], 1/2], [[18, 17], 1/2]]) 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: f1feb91f18ba811d2876a68789bcf886a645ffda044bd324a4bdc2ca92041f18 - candidate record SHA-256: db89941266a9d81076962576aec0ca0172a3ac2987327cae791e7d24e3070df3 - semantic review receipt SHA-256: b4c47938fd38085d44967226cfa8337d61334455472e7307c60d3a488cef598f - question-first witness SHA-256: 3c23baa97a5933bc07b44f2257017ef4e845bf1429bd6f5381410681c43b97e4 - Lean: NOT_RUN · human review: NOT_PERFORMED [Same-source full JSON](https://ocme.evemisslab.com/data/question-derivations/questions/q-20261013-advance-20261023-r06-discrete-stochastic-process-0093.json)