---
_id: '12738'
abstract:
- lang: eng
  text: We study turn-based stochastic zero-sum games with lexicographic preferences
    over objectives. Stochastic games are standard models in control, verification,
    and synthesis of stochastic reactive systems that exhibit both randomness as well
    as controllable and adversarial non-determinism. Lexicographic order allows one
    to consider multiple objectives with a strict preference order. To the best of
    our knowledge, stochastic games with lexicographic objectives have not been studied
    before. For a mixture of reachability and safety objectives, we show that deterministic
    lexicographically optimal strategies exist and memory is only required to remember
    the already satisfied and violated objectives. For a constant number of objectives,
    we show that the relevant decision problem is in NP∩coNP, matching the current
    known bound for single objectives; and in general the decision problem is PSPACE-hard
    and can be solved in NEXPTIME∩coNEXPTIME. We present an algorithm that computes
    the lexicographically optimal strategies via a reduction to the computation of
    optimal strategies in a sequence of single-objectives games. For omega-regular
    objectives, we restrict our analysis to one-player games, also known as Markov
    decision processes. We show that lexicographically optimal strategies exist and
    need either randomization or finite memory. We present an algorithm that solves
    the relevant decision problem in polynomial time. We have implemented our algorithms
    and report experimental results on various case studies.
acknowledgement: Tobias Winkler and Joost-Pieter Katoen are supported by the DFG RTG
  2236 UnRAVeL and the innovation programme under the Marie Skłodowska-Curie grant
  agreement No. 101008233 (Mission). Krishnendu Chatterjee is supported by the ERC
  CoG 863818 (ForM-SMArt) and the Vienna Science and Technology Fund (WWTF) Project
  ICT15-003. Maximilian Weininger is supported by the DFG projects 383882557 Statistical
  Unbounded Verification (SUV) and 427755713 Group-By Objectives in Probabilistic
  Verification (GOPro). Stefanie Mohr is supported by the DFG RTG 2428 CONVEY. Open
  Access funding enabled and organized by Projekt DEAL.
article_processing_charge: No
article_type: original
author:
- first_name: Krishnendu
  full_name: Chatterjee, Krishnendu
  id: 2E5DCA20-F248-11E8-B48F-1D18A9856A87
  last_name: Chatterjee
  orcid: 0000-0002-4561-241X
- first_name: Joost P
  full_name: Katoen, Joost P
  id: 4524F760-F248-11E8-B48F-1D18A9856A87
  last_name: Katoen
- first_name: Stefanie
  full_name: Mohr, Stefanie
  last_name: Mohr
- first_name: Maximilian
  full_name: Weininger, Maximilian
  last_name: Weininger
- first_name: Tobias
  full_name: Winkler, Tobias
  last_name: Winkler
citation:
  ama: Chatterjee K, Katoen JP, Mohr S, Weininger M, Winkler T. Stochastic games with
    lexicographic objectives. <i>Formal Methods in System Design</i>. 2023. doi:<a
    href="https://doi.org/10.1007/s10703-023-00411-4">10.1007/s10703-023-00411-4</a>
  apa: Chatterjee, K., Katoen, J. P., Mohr, S., Weininger, M., &#38; Winkler, T. (2023).
    Stochastic games with lexicographic objectives. <i>Formal Methods in System Design</i>.
    Springer Nature. <a href="https://doi.org/10.1007/s10703-023-00411-4">https://doi.org/10.1007/s10703-023-00411-4</a>
  chicago: Chatterjee, Krishnendu, Joost P Katoen, Stefanie Mohr, Maximilian Weininger,
    and Tobias Winkler. “Stochastic Games with Lexicographic Objectives.” <i>Formal
    Methods in System Design</i>. Springer Nature, 2023. <a href="https://doi.org/10.1007/s10703-023-00411-4">https://doi.org/10.1007/s10703-023-00411-4</a>.
  ieee: K. Chatterjee, J. P. Katoen, S. Mohr, M. Weininger, and T. Winkler, “Stochastic
    games with lexicographic objectives,” <i>Formal Methods in System Design</i>.
    Springer Nature, 2023.
  ista: Chatterjee K, Katoen JP, Mohr S, Weininger M, Winkler T. 2023. Stochastic
    games with lexicographic objectives. Formal Methods in System Design.
  mla: Chatterjee, Krishnendu, et al. “Stochastic Games with Lexicographic Objectives.”
    <i>Formal Methods in System Design</i>, Springer Nature, 2023, doi:<a href="https://doi.org/10.1007/s10703-023-00411-4">10.1007/s10703-023-00411-4</a>.
  short: K. Chatterjee, J.P. Katoen, S. Mohr, M. Weininger, T. Winkler, Formal Methods
    in System Design (2023).
date_created: 2023-03-19T23:00:59Z
date_published: 2023-03-08T00:00:00Z
date_updated: 2025-07-14T09:10:14Z
day: '08'
ddc:
- '000'
department:
- _id: KrCh
doi: 10.1007/s10703-023-00411-4
ec_funded: 1
external_id:
  isi:
  - '000946174300001'
isi: 1
language:
- iso: eng
main_file_link:
- open_access: '1'
  url: https://doi.org/10.1007/s10703-023-00411-4
month: '03'
oa: 1
oa_version: Published Version
project:
- _id: 0599E47C-7A3F-11EA-A408-12923DDC885E
  call_identifier: H2020
  grant_number: '863818'
  name: 'Formal Methods for Stochastic Models: Algorithms and Applications'
- _id: 25892FC0-B435-11E9-9278-68D0E5697425
  grant_number: ICT15-003
  name: Efficient Algorithms for Computer Aided Verification
publication: Formal Methods in System Design
publication_identifier:
  eissn:
  - 1572-8102
publication_status: epub_ahead
publisher: Springer Nature
quality_controlled: '1'
related_material:
  record:
  - id: '8272'
    relation: earlier_version
    status: public
scopus_import: '1'
status: public
title: Stochastic games with lexicographic objectives
tmp:
  image: /images/cc_by.png
  legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
  name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
  short: CC BY (4.0)
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
year: '2023'
...
---
_id: '8272'
abstract:
- lang: eng
  text: We study turn-based stochastic zero-sum games with lexicographic preferences
    over reachability and safety objectives. Stochastic games are standard models
    in control, verification, and synthesis of stochastic reactive systems that exhibit
    both randomness as well as angelic and demonic non-determinism. Lexicographic
    order allows to consider multiple objectives with a strict preference order over
    the satisfaction of the objectives. To the best of our knowledge, stochastic games
    with lexicographic objectives have not been studied before. We establish determinacy
    of such games and present strategy and computational complexity results. For strategy
    complexity, we show that lexicographically optimal strategies exist that are deterministic
    and memory is only required to remember the already satisfied and violated objectives.
    For a constant number of objectives, we show that the relevant decision problem
    is in   NP∩coNP , matching the current known bound for single objectives; and
    in general the decision problem is   PSPACE -hard and can be solved in   NEXPTIME∩coNEXPTIME
    . We present an algorithm that computes the lexicographically optimal strategies
    via a reduction to computation of optimal strategies in a sequence of single-objectives
    games. We have implemented our algorithm and report experimental results on various
    case studies.
alternative_title:
- LNCS
article_processing_charge: No
arxiv: 1
author:
- first_name: Krishnendu
  full_name: Chatterjee, Krishnendu
  id: 2E5DCA20-F248-11E8-B48F-1D18A9856A87
  last_name: Chatterjee
  orcid: 0000-0002-4561-241X
- first_name: Joost P
  full_name: Katoen, Joost P
  id: 4524F760-F248-11E8-B48F-1D18A9856A87
  last_name: Katoen
- first_name: Maximilian
  full_name: Weininger, Maximilian
  last_name: Weininger
- first_name: Tobias
  full_name: Winkler, Tobias
  last_name: Winkler
citation:
  ama: 'Chatterjee K, Katoen JP, Weininger M, Winkler T. Stochastic games with lexicographic
    reachability-safety objectives. In: <i>International Conference on Computer Aided
    Verification</i>. Vol 12225. Springer Nature; 2020:398-420. doi:<a href="https://doi.org/10.1007/978-3-030-53291-8_21">10.1007/978-3-030-53291-8_21</a>'
  apa: Chatterjee, K., Katoen, J. P., Weininger, M., &#38; Winkler, T. (2020). Stochastic
    games with lexicographic reachability-safety objectives. In <i>International Conference
    on Computer Aided Verification</i> (Vol. 12225, pp. 398–420). Springer Nature.
    <a href="https://doi.org/10.1007/978-3-030-53291-8_21">https://doi.org/10.1007/978-3-030-53291-8_21</a>
  chicago: Chatterjee, Krishnendu, Joost P Katoen, Maximilian Weininger, and Tobias
    Winkler. “Stochastic Games with Lexicographic Reachability-Safety Objectives.”
    In <i>International Conference on Computer Aided Verification</i>, 12225:398–420.
    Springer Nature, 2020. <a href="https://doi.org/10.1007/978-3-030-53291-8_21">https://doi.org/10.1007/978-3-030-53291-8_21</a>.
  ieee: K. Chatterjee, J. P. Katoen, M. Weininger, and T. Winkler, “Stochastic games
    with lexicographic reachability-safety objectives,” in <i>International Conference
    on Computer Aided Verification</i>, 2020, vol. 12225, pp. 398–420.
  ista: 'Chatterjee K, Katoen JP, Weininger M, Winkler T. 2020. Stochastic games with
    lexicographic reachability-safety objectives. International Conference on Computer
    Aided Verification. CAV: Computer Aided Verification, LNCS, vol. 12225, 398–420.'
  mla: Chatterjee, Krishnendu, et al. “Stochastic Games with Lexicographic Reachability-Safety
    Objectives.” <i>International Conference on Computer Aided Verification</i>, vol.
    12225, Springer Nature, 2020, pp. 398–420, doi:<a href="https://doi.org/10.1007/978-3-030-53291-8_21">10.1007/978-3-030-53291-8_21</a>.
  short: K. Chatterjee, J.P. Katoen, M. Weininger, T. Winkler, in:, International
    Conference on Computer Aided Verification, Springer Nature, 2020, pp. 398–420.
conference:
  name: 'CAV: Computer Aided Verification'
date_created: 2020-08-16T22:00:58Z
date_published: 2020-07-14T00:00:00Z
date_updated: 2025-07-14T09:10:14Z
day: '14'
ddc:
- '000'
department:
- _id: KrCh
doi: 10.1007/978-3-030-53291-8_21
ec_funded: 1
external_id:
  arxiv:
  - '2005.04018'
  isi:
  - '000695272500021'
file:
- access_level: open_access
  checksum: 093d4788d7d5b2ce0ffe64fbe7820043
  content_type: application/pdf
  creator: dernst
  date_created: 2020-08-17T11:32:44Z
  date_updated: 2020-08-17T11:32:44Z
  file_id: '8276'
  file_name: 2020_LNCS_CAV_Chatterjee.pdf
  file_size: 625056
  relation: main_file
  success: 1
file_date_updated: 2020-08-17T11:32:44Z
has_accepted_license: '1'
intvolume: '     12225'
isi: 1
language:
- iso: eng
month: '07'
oa: 1
oa_version: Published Version
page: 398-420
project:
- _id: 0599E47C-7A3F-11EA-A408-12923DDC885E
  call_identifier: H2020
  grant_number: '863818'
  name: 'Formal Methods for Stochastic Models: Algorithms and Applications'
- _id: 25892FC0-B435-11E9-9278-68D0E5697425
  grant_number: ICT15-003
  name: Efficient Algorithms for Computer Aided Verification
publication: International Conference on Computer Aided Verification
publication_identifier:
  eissn:
  - '16113349'
  isbn:
  - '9783030532901'
  issn:
  - '03029743'
publication_status: published
publisher: Springer Nature
quality_controlled: '1'
related_material:
  record:
  - id: '12738'
    relation: later_version
    status: public
scopus_import: '1'
status: public
title: Stochastic games with lexicographic reachability-safety objectives
tmp:
  image: /images/cc_by.png
  legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
  name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
  short: CC BY (4.0)
type: conference
user_id: 4359f0d1-fa6c-11eb-b949-802e58b17ae8
volume: 12225
year: '2020'
...
---
_id: '79'
abstract:
- lang: eng
  text: 'Markov Decision Processes (MDPs) are a popular class of models suitable for
    solving control decision problems in probabilistic reactive systems. We consider
    parametric MDPs (pMDPs) that include parameters in some of the transition probabilities
    to account for stochastic uncertainties of the environment such as noise or input
    disturbances. We study pMDPs with reachability objectives where the parameter
    values are unknown and impossible to measure directly during execution, but there
    is a probability distribution known over the parameter values. We study for the
    first time computing parameter-independent strategies that are expectation optimal,
    i.e., optimize the expected reachability probability under the probability distribution
    over the parameters. We present an encoding of our problem to partially observable
    MDPs (POMDPs), i.e., a reduction of our problem to computing optimal strategies
    in POMDPs. We evaluate our method experimentally on several benchmarks: a motivating
    (repeated) learner model; a series of benchmarks of varying configurations of
    a robot moving on a grid; and a consensus protocol.'
alternative_title:
- LNCS
article_processing_charge: No
arxiv: 1
author:
- first_name: Sebastian
  full_name: Arming, Sebastian
  last_name: Arming
- first_name: Ezio
  full_name: Bartocci, Ezio
  last_name: Bartocci
- first_name: Krishnendu
  full_name: Chatterjee, Krishnendu
  id: 2E5DCA20-F248-11E8-B48F-1D18A9856A87
  last_name: Chatterjee
  orcid: 0000-0002-4561-241X
- first_name: Joost P
  full_name: Katoen, Joost P
  id: 4524F760-F248-11E8-B48F-1D18A9856A87
  last_name: Katoen
- first_name: Ana
  full_name: Sokolova, Ana
  last_name: Sokolova
citation:
  ama: 'Arming S, Bartocci E, Chatterjee K, Katoen JP, Sokolova A. Parameter-independent
    strategies for pMDPs via POMDPs. In: Vol 11024. Springer; 2018:53-70. doi:<a href="https://doi.org/10.1007/978-3-319-99154-2_4">10.1007/978-3-319-99154-2_4</a>'
  apa: 'Arming, S., Bartocci, E., Chatterjee, K., Katoen, J. P., &#38; Sokolova, A.
    (2018). Parameter-independent strategies for pMDPs via POMDPs (Vol. 11024, pp.
    53–70). Presented at the QEST: Quantitative Evaluation of Systems, Beijing, China:
    Springer. <a href="https://doi.org/10.1007/978-3-319-99154-2_4">https://doi.org/10.1007/978-3-319-99154-2_4</a>'
  chicago: Arming, Sebastian, Ezio Bartocci, Krishnendu Chatterjee, Joost P Katoen,
    and Ana Sokolova. “Parameter-Independent Strategies for PMDPs via POMDPs,” 11024:53–70.
    Springer, 2018. <a href="https://doi.org/10.1007/978-3-319-99154-2_4">https://doi.org/10.1007/978-3-319-99154-2_4</a>.
  ieee: 'S. Arming, E. Bartocci, K. Chatterjee, J. P. Katoen, and A. Sokolova, “Parameter-independent
    strategies for pMDPs via POMDPs,” presented at the QEST: Quantitative Evaluation
    of Systems, Beijing, China, 2018, vol. 11024, pp. 53–70.'
  ista: 'Arming S, Bartocci E, Chatterjee K, Katoen JP, Sokolova A. 2018. Parameter-independent
    strategies for pMDPs via POMDPs. QEST: Quantitative Evaluation of Systems, LNCS,
    vol. 11024, 53–70.'
  mla: Arming, Sebastian, et al. <i>Parameter-Independent Strategies for PMDPs via
    POMDPs</i>. Vol. 11024, Springer, 2018, pp. 53–70, doi:<a href="https://doi.org/10.1007/978-3-319-99154-2_4">10.1007/978-3-319-99154-2_4</a>.
  short: S. Arming, E. Bartocci, K. Chatterjee, J.P. Katoen, A. Sokolova, in:, Springer,
    2018, pp. 53–70.
conference:
  end_date: 2018-09-07
  location: Beijing, China
  name: 'QEST: Quantitative Evaluation of Systems'
  start_date: 2018-09-04
date_created: 2018-12-11T11:44:31Z
date_published: 2018-08-15T00:00:00Z
date_updated: 2023-09-13T09:38:28Z
day: '15'
department:
- _id: KrCh
- _id: ToHe
doi: 10.1007/978-3-319-99154-2_4
external_id:
  arxiv:
  - '1806.05126'
  isi:
  - '000548912200004'
intvolume: '     11024'
isi: 1
language:
- iso: eng
main_file_link:
- open_access: '1'
  url: https://arxiv.org/abs/1806.05126
month: '08'
oa: 1
oa_version: Preprint
page: 53-70
publication_status: published
publisher: Springer
publist_id: '7975'
quality_controlled: '1'
scopus_import: '1'
status: public
title: Parameter-independent strategies for pMDPs via POMDPs
type: conference
user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1
volume: 11024
year: '2018'
...
---
_id: '10418'
abstract:
- lang: eng
  text: We present a new proof rule for proving almost-sure termination of probabilistic
    programs, including those that contain demonic non-determinism. An important question
    for a probabilistic program is whether the probability mass of all its diverging
    runs is zero, that is that it terminates "almost surely". Proving that can be
    hard, and this paper presents a new method for doing so. It applies directly to
    the program's source code, even if the program contains demonic choice. Like others,
    we use variant functions (a.k.a. "super-martingales") that are real-valued and
    decrease randomly on each loop iteration; but our key innovation is that the amount
    as well as the probability of the decrease are parametric. We prove the soundness
    of the new rule, indicate where its applicability goes beyond existing rules,
    and explain its connection to classical results on denumerable (non-demonic) Markov
    chains.
acknowledgement: "McIver and Morgan are grateful to David Basin and the Information
  Security Group at ETH Zürich for hosting a six-month stay in Switzerland, during
  part of which this work began. And thanks particularly to Andreas Lochbihler, who
  shared with us the probabilistic termination problem that led to it. They acknowledge
  the support of ARC grant DP140101119. Part of this work was carried out during the
  Workshop on Probabilistic Programming Semantics\r\nat McGill University’s Bellairs
  Research Institute on Barbados organised by Alexandra Silva and\r\nPrakash Panangaden.
  Kaminski and Katoen are grateful to Sebastian Junges for spotting a flaw in §5.4."
article_number: '33'
article_processing_charge: No
article_type: original
arxiv: 1
author:
- first_name: Annabelle
  full_name: Mciver, Annabelle
  last_name: Mciver
- first_name: Carroll
  full_name: Morgan, Carroll
  last_name: Morgan
- first_name: Benjamin Lucien
  full_name: Kaminski, Benjamin Lucien
  last_name: Kaminski
- first_name: Joost P
  full_name: Katoen, Joost P
  id: 4524F760-F248-11E8-B48F-1D18A9856A87
  last_name: Katoen
citation:
  ama: Mciver A, Morgan C, Kaminski BL, Katoen JP. A new proof rule for almost-sure
    termination. <i>Proceedings of the ACM on Programming Languages</i>. 2017;2(POPL).
    doi:<a href="https://doi.org/10.1145/3158121">10.1145/3158121</a>
  apa: 'Mciver, A., Morgan, C., Kaminski, B. L., &#38; Katoen, J. P. (2017). A new
    proof rule for almost-sure termination. <i>Proceedings of the ACM on Programming
    Languages</i>. Los Angeles, CA, United States: Association for Computing Machinery.
    <a href="https://doi.org/10.1145/3158121">https://doi.org/10.1145/3158121</a>'
  chicago: Mciver, Annabelle, Carroll Morgan, Benjamin Lucien Kaminski, and Joost
    P Katoen. “A New Proof Rule for Almost-Sure Termination.” <i>Proceedings of the
    ACM on Programming Languages</i>. Association for Computing Machinery, 2017. <a
    href="https://doi.org/10.1145/3158121">https://doi.org/10.1145/3158121</a>.
  ieee: A. Mciver, C. Morgan, B. L. Kaminski, and J. P. Katoen, “A new proof rule
    for almost-sure termination,” <i>Proceedings of the ACM on Programming Languages</i>,
    vol. 2, no. POPL. Association for Computing Machinery, 2017.
  ista: Mciver A, Morgan C, Kaminski BL, Katoen JP. 2017. A new proof rule for almost-sure
    termination. Proceedings of the ACM on Programming Languages. 2(POPL), 33.
  mla: Mciver, Annabelle, et al. “A New Proof Rule for Almost-Sure Termination.” <i>Proceedings
    of the ACM on Programming Languages</i>, vol. 2, no. POPL, 33, Association for
    Computing Machinery, 2017, doi:<a href="https://doi.org/10.1145/3158121">10.1145/3158121</a>.
  short: A. Mciver, C. Morgan, B.L. Kaminski, J.P. Katoen, Proceedings of the ACM
    on Programming Languages 2 (2017).
conference:
  end_date: 2018-01-13
  location: Los Angeles, CA, United States
  name: 'POPL: Programming Languages'
  start_date: 2018-01-07
date_created: 2021-12-05T23:01:49Z
date_published: 2017-12-07T00:00:00Z
date_updated: 2021-12-07T08:04:14Z
day: '07'
department:
- _id: KrCh
- _id: ToHe
doi: 10.1145/3158121
external_id:
  arxiv:
  - '1711.03588'
intvolume: '         2'
issue: POPL
language:
- iso: eng
main_file_link:
- open_access: '1'
  url: https://dl.acm.org/doi/10.1145/3158121
month: '12'
oa: 1
oa_version: Published Version
publication: Proceedings of the ACM on Programming Languages
publication_identifier:
  eissn:
  - 2475-1421
publication_status: published
publisher: Association for Computing Machinery
quality_controlled: '1'
scopus_import: '1'
status: public
title: A new proof rule for almost-sure termination
type: journal_article
user_id: 8b945eb4-e2f2-11eb-945a-df72226e66a9
volume: 2
year: '2017'
...
