- Spot - LRE

Bug when checking for automata emptiness in print_hoa()
by Beutner, Raven 04 Jan '23

04 Jan '23

Dear spot Team, I think I have found a bug in the emptiness checker of spot. When I use the following automation: HOA: v1 States: 8 Start: 0 Start: 1 AP: 0 acc-name: generalized-Buchi 2 Acceptance: 2 Inf(0)&Inf(1) --BODY-- State: 0 {0} [(t)] 2 [(t)] 3 State: 1 {0} [(t)] 4 [(t)] 5 State: 2 {0} [(t)] 2 [(t)] 3 State: 3 {0} [(t)] 6 [(t)] 7 State: 4 {1} [(t)] 4 [(t)] 5 State: 5 {1} [(t)] 6 [(t)] 7 State: 6 [(t)] 6 [(t)] 7 State: 7 [(t)] 6 [(t)] 7 --END-- And invoke "autfilt --is-empty aut.hoa” (where aut.hoa contains the above automaton) I get the following error: autfilt: print_hoa(): automaton has transition-based acceptance despite prop_state_acc()==true This seems to be related to a similar bug that was fixed in version 2.7.1, so should (hopefully) be easy to fix. I used version 2.11.3 on a MacBook Pro with M1 Pro CPU. All the best, Raven

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[CfP]: On the Effectiveness of Temporal Logics on Finite Traces in AI
by Antonio Di Stasio 24 Dec '22

24 Dec '22

CALL FOR PAPERS "On the Effectiveness of Temporal Logics on Finite Traces in AI" Part of the AAAI 2023 Spring Symposium Series <https://aaai.org/Symposia/Spring/sss23.php> March 27-29, 2023, Hyatt Regency San Francisco Airport, CA, USA Website: https://ltlf-symposium.github.io/ Temporal logics, such as Linear Temporal Logic (LTL), are widely adopted as a logical specification language in Formal Methods. They are also getting increasing attention from the AI Community. In AI, however, there is often a need to interpret such logics over finite traces, rather than the traditional infinite-trace interpretation. This is evident, for instance, in works on Planning, Reinforcement Learning, and Business Process Management. An important computational feature of working with finite traces is that it allows one to use standard finite-state automata to model and reason, rather than the more complex omega-automata used for infinite traces. This is a great simplification that has already had a significant impact on many areas of AI and CS. This symposium aims to bring together researchers working with temporal logics on finite traces, in basic research and applications, in order to discuss current results and future directions, and to facilitate the emergence of teams working across different areas. Topics Topics of interest span the use of temporal logics over finite traces, including (but not limited to) the following areas: - AI Planning - Verification and Synthesis - Reinforcement Learning - Automated Reasoning - Knowledge Representation - Multi-Agent Systems - Robotics - Motion and Task Planning - Discrete-Event Control - Workflow Management - Conversational Systems - Automated Service Composition - Business Process Management - Fintech - Cyber Security - Human Computer Interaction - Natural Language Processing Submissions Submissions should have a single main author, who will be the speaker, and each speaker can have no more than one submission. Each submission must not exceed 2 pages, including references (in AAAI style), and may refer to joint work with other collaborators to be credited in the presentation. There will be no formal proceedings and we encourage submissions of work presented or submitted elsewhere (no copyright transfer is required, only permission to post the abstract on the workshop site). Submissions should be uploaded via the AAAI SSS-23 EasyChair site. <https://easychair.org/conferences/?conf=sss23> Important Dates - January 30, 2023: Paper submission deadline (AoE). - February 4, 2023: Author notification (AoE). - March 27-29: AAAI Spring Symposium Series. Invited Speakers - Rance Cleaveland <https://www.cs.umd.edu/people/wcleavel>, University of Maryland, USA - Giuseppe De Giacomo <https://www.diag.uniroma1.it//degiacom/>, University of Oxford & Sapienza University of Rome, Italy - Lydia Kavraki <https://www.cs.rice.edu/~kavraki/>, Rice University, Houston, TX, USA - Shiela A. Mcilraith <https://www.cs.toronto.edu/~sheila/>, University of Toronto, Canada - Marco Montali <https://www.unibz.it/it/faculties/computer-science/academic-staff/person/31…>, University of Bolzano, Italy - Kristin Y. Rozier <https://www.engineering.iastate.edu/people/profile/kyrozier/>, Iowa State University, USA - Ufuk Topcu <https://www.ae.utexas.edu/people/faculty/faculty-directory/topcu>, University of Texas at Austin, TX, USA - Moshe Vardi <https://www.cs.rice.edu/~vardi/>, Rice University, Houston, TX, USA Organizing Committee - Suguman Bansal <https://suguman.github.io/>, Co-Chair, Georgia Institute of Technology, suguman(a)seas.upenn.edu - Antonio Di Stasio <https://antoniodistasio.github.io/>, Co-Chair, Sapienza University of Rome, distasio(a)diag.uniroma1.it - Sasha Rubin <https://sasharubin.github.io/>, Co-Chair, University of Sydney, sasha.rubin(a)sydney.edu.au - Shufang Zhu <https://shufang-zhu.github.io/>, Co-Chair, Sapienza University of Rome, zhu(a)diag.uniroma1.it Website For more information, please see the symposium website: https://ltlf-symposium.github.io/

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Generating unsatisfiable LTL formulae using randltl
by Pert, Charles 12 Dec '22

12 Dec '22

Hi, I am specifically trying to generate unsatisfiable LTL formulae using the randltl tool in Spot. I am struggling because the default tool is so much more likely to produce consistent and satisfiable formulae. Have you got any tips on how I can alter the generation to produce these types of formulae? Best wishes, Charles Pert

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Bug report: implication prefix
by Liu, Jason Xinyu 30 Nov '22

30 Nov '22

Hello, It seems that Spot cannot parse implication and equivalent operators in prefix order. I tried on both my local machine and the online translator <https://spot.lre.epita.fr/app/>. The installed Spot version is 2.11.1. The commands are - local: spot.formula("-> a b") - online translator: type in -> a b Error message: syntax error, unexpected implication operator Thank you very much for your help and creating the conda package for Spot, that makes the installation very convenient! Happy holidays! Best, Jason

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[bug] ltl2tgba gets stuck with this formula
by Jacopo Binchi 31 Oct '22

31 Oct '22

Dear Spot support team, I am a researcher at Developair Technologies. I write you looking for help with a formula that ltl2tgba cannot handle, possibly a bug. Here at Developair we have been using Spot for the past few months with great satisfaction. However, it seems that *ltl2tgba *cannot process the formula in attached file gb_formula.ltl . We let it run for quite some time (like hours) and it didn't terminate. On the other hand, Owl can process the same formula in a matter of a few milliseconds. We don't have any problem using ltl2tgba with other, similar formulas. It seems strange to us that Spot gets stuck with such a relatively simple formula, especially since in our experience Spot worked reliably well with other, way more complex formulas. Is it maybe a bug or something that we are doing wrong? Could you please help us? Please find some more details (version and command) below. Thank you. Best regards, J. Spot version: ltl2tgba --version > ltl2tgba (spot) 2.10.6 > > Copyright (C) 2022 Laboratoire de Recherche et Développement de l'Epita. > License GPLv3+: GNU GPL version 3 or later < > http://gnu.org/licenses/gpl.html>. > This is free software: you are free to change and redistribute it. > There is NO WARRANTY, to the extent permitted by law. > Command: ltl2tgba -S --deterministic --dot=s --output=output.txt -F gb_formula.ltl Using the "simplest" command "ltl2tgba -F gb_formula.ltl" produces the same result (that is, no result). For comparison, with Owl we used command: owl ltl2ldgba --state-acceptance -i gb_formula.ltl -o owl_gb.txt -- Jacopo Binchi jbinchi(a)developair.es Paseo de Miramón 170 20014 San Sebastián – Donostia Gipuzkoa (Spain) www.developair.es

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Number of states and transitions
by pierreganty＠gmail.com 28 Oct '22

28 Oct '22

Hi all, I did not find how to get the number of states (reachable or not) of an automaton using autfilt (in particular the `--stats` option). The option provided by `autfilt --stats` is for reachable states only. I did find a workaround with `--hoaf` which outputs the automaton in HOA format and then getting the number from the `States:` header. For the number of transitions (reachable or not) I don't have a workaround. Since spot can compute these numbers easily, it seems handy (at least for me) to have a direct access to them thru the `--stats` interface. Thank you, Pierre.

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Issue with Debian package signature
by Ocan Sankur 07 Oct '22

07 Oct '22

Hi all, I am trying to install spot on Ubuntu 20.04 following instructions from: https://spot.lrde.epita.fr/install.html But apt update complains about the signature: W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://www.lrde.epita.fr/repo/debian stable/ InRelease: The following signatures were invalid: EXPKEYSIG 03D99E7444F2A84A LRDE Repository <admin(a)lrde.epita.fr> W: Failed to fetch http://www.lrde.epita.fr/repo/debian/stable/InRelease The following signatures were invalid: EXPKEYSIG 03D99E7444F2A84A LRDE Repository <admin(a)lrde.epita.fr> Could the signature be expired? I can actually install spot from source but Debian packages are useful for preparing artifact submissions. Thanks, Ocan

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How to identify invalid transitions
by Raven Rothkopf 05 Aug '22

05 Aug '22

Dear Spot developers, Thank you so much for your helpful tool! We are undergraduate researchers at Barnard college and are using your tool for our summer research project. We are writing to ask if you would be able to help us understand a behavior of spot on a spec we are working with. We have the following small spec: ASSUME { G (! ((i1) && (i2))); } GUARANTEE { G (((o1) && (! (o2))) || ((o2) && (! (o1)))); (G (! ((i1) && (i2)))) -> (G (F (o2))); } From this, ltlsynt gives us: AP: 4 "i1" "i2" "o1" "o2" acc-name: all Acceptance: 0 t properties: trans-labels explicit-labels state-acc deterministic --BODY-- State: 0 [0&1&!2&!3 | 0&1&2&3] 0 [!0&!2&3 | !1&!2&3] 0 --END– Due to the ASSUME { G (! ((i1) && (i2)));}, the first transition in the hoa output should never happen. We understand that if a transition violates an assumption, it's still generated in hoa format because the system is free to choose any behavior and make any update. Some questions we have are: how does spot figure out if an assumption has been violated? Is there a flag that spot gives a transition that violates an assumption so that it can be dealt with differently? Instead of generating every possible behavior for the invalid transition, we are interested in removing it altogether. Is this possible to do through spot or do we need to come up with our own postprocessing algorithm? For context, we are working on a tool that takes a spec written in temporal logic and generates program code in a mealy machine format. We want to optimize the generated code so that it is as human-readable as possible. We appreciate any advice you can provide! Best, Leyi and Raven

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Kripke, twa_product and twa_graph
by Pierre 22 Jun '22

22 Jun '22

Dear Spot devs, I am not sure how I am supposed to work with Kripke structures (which I imported using ltsmin) or `twa_product` (which I obtained using `otf_product` on the Kripke structure). In the screenshot below I can invoke 'exclusive_word' with no problems on a `kripke` and `twa_product` but the same is not true for 'contains' which returns a type error. The way I found to invoke 'contains' without errors is to use 'save' and then 'automaton' to read that same file again in order to get `twa_graph` as expected by `contains`. I am not sure this workaround is what the devs had in mind. Thank you for clarifying, PierreG [image: image.png]

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Alphabet abstraction
by Pierre 04 Jun '22

04 Jun '22

Dear Spot devs, Is there a way for Spot to perform the alphabet abstraction available in GOAL as triggered with the `-a` switch when invoking the `alphabet` command? I paste the GOAL documentation about it below. Thank you, Pierre. - Alphabet -NAMEalphabet - Manipulate the alphabet of an automaton or a game.SYNOPSISalphabet -s [ -ap ] FILE_OR_LVALalphabet -e EXPR [ -ap ] FILE_OR_LVALalphabet -c EXPR [ -ap ] FILE_OR_LVALalphabet -r EXPR [ -ap ] FILE_OR_LVALalphabet -a EXPR [-R | -A | -S EXPR | -P EXPR | -ap ] FILE_OR_LVALDESCRIPTIONManipulate the alphabet of an automaton (or a game). This operation is directly applied to the input automaton. The returned value is always the new alphabet of the automaton (or the new atomic propositions if -ap is present). -s Simply return the alphabet of the input automaton or game. -ap Return the atomic propositions (or classical symbols) instead of the alphabet. -e Expand the alphabet by a list of propositions. -c Contract the alphabet by removing a list of propositions. -r Rename the propositions based on a map from a proposition to its new name. -a Abstract the alphabet based on a map from a predicate to its definition. -R Retain the transition symbols in alphabet abstraction. -A Only annotate the transitions with properties specified by -S and -P. -S Specify the name of the property that will store the symbols on the transitions in alphabet abstraction. -P Specify the name of the property that will store the evaluations of the predicates in alphabet abstraction. EXAMPLE alphabet -e "r" aut.gff alphabet -c "p" aut.gff alphabet -r "p=>r,q=>s" aut.gff alphabet -a "r=>p/\q" aut.gff alphabet -a "r=>p/\q" -A -P "Predicates" aut.gff

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