- Spot - LRE

how to add new features to spot
by 李建文 19 Jun '12

19 Jun '12

Dear sir: I am trying to extend spot by adding a new ltl-to-ba translation algorithm. The brief idea is that I extend the formula structure in spot so that I can use the parser for ltl formulas. Now I have finished the code and want to compile my codes with those in spot, but I am confused how I can achieve this. Does spot provides some interfaces that can help someone to extend it? Thanks very much for attention and I am expecting your reply. Best Jianwen

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TGBA Doubt
by Agrawal, Akshay 19 Jun '12

19 Jun '12

Hi, I am a Grad Student at Vanderbilt University,TN,USA and am working on formal verification of software systems. I was using spot library and your site and wanted to know : if a TGBA ( Transition based generalized Buchi automaton) has all transitions as accepting transitions by definition then what is this {ACC[r]} condition that explicitly appears ion automaton when I write LTL formula : F r. And why don't I get any such thing when I use LTL formula : X r. I will appreciate your reply. Thanks in advance, Akshay Agrawal

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spot using help
by Jianwen Li 11 Jun '12

11 Jun '12

Dear sir: I recently try to implement the algorithm translating LTL formulas to Buchi automata in the SPOT framework. When I read the source codes of SPOT I was confused about the structure of the automaton. How did you store the transitions and states in the automaton, such as tgba? I am sorry I can't catch you since I do not see any structure storing them when you define the tgba (tgba.hh, tgba.cc). Thank you for your attention. Best Jianwen

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Spot 0.9 is released
by Alexandre Duret-Lutz 09 May '12

09 May '12

We are pleased to announce the release of Spot 0.9. Spot is a model-checking library developed collaboratively by LRDE and LIP6. It provides algorithms and data structures to implement the automata-theoretic approach to LTL model checking. You can find the new release here: http://spot.lip6.fr/dl/spot-0.9.tar.gz (11MB) The major news in this release are all related to the logic-to-Büchi-automaton translation engine: 1. The linear-time fragment of PSL is supported. This first implementation, enough to experiment with the logic, shall be improved in future versions. (Feedback most welcome.) 2. The LTL simplification code has been overhauled and augmented with new rules. 3. A new simulation-based post-processing can be used to simplify the TGBA constructed. For more details about the first two points (supported operators, and rewritings performed), please read the file doc/tl/tl.pdf included in spot-0.9.tar.gz. A consequence of the last two points is that Spot 0.9 is faster than Spot 0.8.3 and can produce even smaller automata. For some comparative benchmarks, please download http://spot.lip6.fr/dl/bench-0.9.pdf Please direct any feedback and questions to <spot(a)lrde.epita.fr>. (Subscribe at https://www.lrde.epita.fr/mailman/listinfo/spot if you wish.) A more detailed list of new features follows. New in spot 0.9 (2012-05-09): * New features: - Operators from the linear fragment of PSL are supported. This basically extends LTL with Sequential Extended Regulat Expressions (SERE), and a couple of operators to bridge SERE and LTL. See doc/tl/tl.pdf for the list of operators and their semantics. - Formula rewritings have been completely revamped, and augmented with rules for PSL operators (and some new LTL rules as well). See doc/tl/tl.pdf for the list of the rewritings implemented. - Some of these rewritings that may produce larger formulas (for instance to rewrite "{a;b;c}" into "a & X(b & Xc)") may be explicitely disabled with a new option. - The src/ltltest/randltl tool can now generate random SEREs and random PSL formulae. - Only one translator (ltl2tgba_fm) has been augmented to translate the new SERE and PSL operators. The internal translation from SERE to DFA is likely to be rewriten in a future version. - A new function, length_boolone(), computes the size of an LTL/PSL formula while considering that any Boolean term has length 1. - The LTL/PSL parser recognizes some UTF-8 characters (like ◇ or ∧) as operators, and some output routines now have an UTF-8 output mode. Tools like randltl and ltl2tgba have gained an -8 option to enable such output. See doc/tl/tl.pdf for the list of recognized codepoints. - A new direct simulation reduction has been implemented. It works directly on TGBAs. It is in src/tgbaalgos/simlation.hh, and it can be tested via ltl2tgba's -RDS option. - unabbreviate_wm() is a function that rewrites the W and M operators of LTL formulae using R and U. This is called whenever we output a formula in Spin syntax. By combining this with the aforementioned PSL rewriting rules, many PSL formulae that use simple SERE can be converted into LTL formulae that can be feed to tools that only understand U and R. The web interface will let you do this. - changes to the on-line translator: + SVG output is available + can display some properties of a formula + new options for direct simulation, larger rewritings, and utf-8 output - configure --without-included-lbtt will prevent LBTT from being configured and built. This helps on systems (such as MinGW) where LBTT cannot be built. The test-suite will skip any LBTT-based test if LBTT is missing. * Interface changes: - Operators ->, <->, U, W, R, and M are now parsed as right-associative to better match the PSL standard. - The constructors for temporal formulae will perform some trivial simplifications based on associativity, commutativity, idempotence, and neutral elements. See doc/tl/tl.pdf for the list of such simplifications. - Formula instances now have many methods to inspect their properties (membership to syntactic classes, absence of X operator, etc...) in constant time. - LTL/PSL formulae are now handled everywhere as 'const formula*' and not just 'formula*'. This reflects the true nature of these (immutable) formula objects, and cleanups a lot of code. Unfortunately, it is a backward incompatible change: you may have to add 'const' to a couple of lines in your code, and change 'ltl::const_vistitor' into 'ltl::visitor' if you have written a custom visitor. - The new entry point for LTL/PSL simplifications is the function ltl_simplifier::simplify() declared in src/ltlvisit/simplify.hh. The ltl_simplifier class implements a cache. Functions such as reduce() or reduce_tau03() are deprecated. - The old game-theory-based implementations for direct and delayed simulation reductions have been removed. The old direct simulation would only work on degeneralized automata, and yet produce results inferior to the new direct simulation introduced in this release. The implementation of delayed simulation was unreliable. The function reduc_tgba_sim() has been kept for compatibility (it calls the new direct simulation whatever the type of simulation requested) and marked as deprecated. ltl2tgba's options -Rd, -RD are gone. Options -R1t, -R1s, -R2s, and -R2t are deprecated and all made equivalent to -RDS. - The tgba_explicit hierarchy has been reorganized in order to make room for sba_explicit classes that share most of the code. The main consequence is that the tgba_explicit type no longuer exists. However the tgba_explicit_number, tgba_explicit_formula, and tgba_explicit_string still do.

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some questions about spot
by Jianwen Li 18 Apr '12

18 Apr '12

Dear Sir (Madam): Recently I am following your spot tool and try to use it to practice some of my ideas on ltl-to-Buchi translation. After reading the manuals I appreciate if you can answer me these questions: 1. Can I use your ltl parser source codes directly to implement my ideas? 2. Does SPOT integrate some ltl generators? Or, Are there any test suits available for me? 3. Does SPOT provide any interface which can generate the Buchi automata from a list of formulas and output them with any format (e.g prolmea or xml ) back to a file? I appreciate this function very much since I do want to compare my results with those from SPOT. ^^ 4. If I have some new idea to implement a new translation, is it possible for me to integrate it to SPOT? (I ask this since I thought SPOT is open :) ) Thank you very much and hope your reply! Best Jianwen Li

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some questions about spot
by Jianwen Li 17 Mar '12

17 Mar '12

Dear Sir(Madam): When I use the SPOT tool online recently I found the truth that the result Buchi automata for such formulas G(F a && F b) from your tool is not a traditional one. Can you explain why? Thank you very much! Best Jianwen Li

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performance of tgba_safra_complementation
by Nikos Gorogiannis 17 Jan '12

17 Jan '12

Hi Alexandre, I have some code that uses the standard pattern for checking language inclusion between two automata, using tgba_safra_complementation. The automata have a small number of states (<100) and one acceptance condition. Running my code under valgrind for time profiling reveals a curious time distribution: 30% of the execution time is spent in malloc and free (20%/10% resp). The call hierarchy is as follows: malloc/free <- operator new/delete <- tgba_tba_proxy::succ_iter <- tgba_sba_proxy ctor <- safra_determinisation::create_safra_automaton <- tgba_safra_complement I have eliminated the contribution of my code to the run time of malloc and free (basically by avoiding creating and destroying the same states repeatedly through memoizing). Is there any workaround to this, i.e., could better/different memory management eliminate this 30% of overhead? Are other complementation algorithms better for this use-case? Best regards Nikos PS What is the preferred way of referencing Spot in a publication?

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spot-beginner questions
by Nikos Gorogiannis 17 Nov '11

17 Nov '11

Hi, I'm trying to learn spot, and I want to run an emptiness check on a product of two automata which I will be creating by subclassing tgba. The two automata have overlapping, but different, signatures i.e. atomic propositions. If I understand correctly, I cannot achieve this by using two different bdd_dicts, as the two automata passed to the product object must share the same bdd_dict. How does one deal with this problem in spot? Thanks Nikos

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self-modifying automaton
by Nikos Gorogiannis 07 Oct '11

07 Oct '11

Hi, I've been looking for a library that would allow me to provide a (lazy) interface for enumerating the states of an automaton and doing on-the-fly model checking. Spot looks like exactly what I need! (which is great; I couldn't find any other tool supporting custom model checking like this). What I will need on top of this, is when the emptiness check fails, I'd like to modify the automaton using the information provided by the check and re-run the check. Changes to the automaton will be localized, so destroying and rebuilding the objects relating to the emptiness check seems unnecessarily expensive. Is there any way around this? Best regards Nikos Gorogiannis

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Nondeterministic behavior of ltl2tgba tool
by Tomáš Babiak 17 Aug '11

17 Aug '11

Dear SPOT developers, I am doing a research on translation of LTL to BA and I am using the tool "ltl2tgba" included in the SPOT 0.7.1 distribution as a reference. While comparing "ltl2tgba" to some other translations using the "lbtt" tool, I have noticed that it sometimes produces different results (regarding the size of produced automata) without changing any parameters. It appers that for some formulae it nondeterministicaly produces different automata. I attach an example when "ltl2tgba" was executed four times in the row always producing a different automaton. First three automata differs only by the names of states or the ordering of transitions, while the last automaton has one state less than the others. However, all automata seam to be correct and mutually equivalent. After a closer examination, it seams that this behavior is caused be the -r7 option enabling tau03 formula reductions. Similar behavior can be observed using -r5 or -r6 options as well. The question is whether such a nondeterminstic behavior is expected while using language containment formula reductions or it is caused by an implementation bug. Thank you for your help. Best regards, Tomas Babiak

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