We are pleased to announce the release of Spot 0.6.
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.
This release adds support for W (weak until) and M (strong release) LTL operators, it also improves LTL rewriting rules as well as the degeneralization algorithm. The result is that a lot of LTL formulae from our benchmark are translated to smaller automata, and the reduction is even more important when producing never claims.
You can find the new release here:
http://spot.lip6.fr/dl/spot-0.6.tar.gz
New in spot 0.6 (16-04-2010):
* Several optimizations to improve some auxiliary steps of the LTL translation (not the core of the translation): - Better degeneralization - SCC simplifications has been tuned for degeneralization (ltl2tgba now has two options -R3 and -R3f: the latter will remove every acceptance condition that used to be removed in Spot 0.5 while the former will leave useless acceptance conditions going to accepting SCC. Experience shows that -R3 is more favorable to degeneralization). - ltl2tgba will perform SCC optimizations before degeneralization and not the converse - We added a syntactic simplification rule to rewrite F(a)|F(b) as F(a|b). We only had a rule for the more specific FG(a)|FG(b) = F(Ga|Gb). - The syntactic simplification rule for F(a&GF(b)) = F(a)&GF(b) has be disabled because the latter formula is in fact harder to translate efficiently. * New LTL operators: W (weak until) and its dual M (strong release) - Weak until allows many LTL specification to be specified more compactly. - All LTL translation algorithms have been updated to support these operators. - Although they do not add any expressive power, translating "a W b" is more efficient (read smaller output automaton) than translating the equivalent form using the U operator. - Basic syntactic rewriting rules will automatically rewrite "a U (b | G(a))" and "(a U b)|G(a)" as "a W b", so you will benefit from the new operators even if you do not use them. Similar rewriting rules exist for R and M, although they are less used. * New options have been added to the CGI script for - SVG output - SCC simplifications * Bug fixes: - The precedence of the "->" and "<->" Boolean operators has been adjusted to better match other tools. Spot <= 0.5 used to parse "a & b -> c & d" as "a & (b -> c) & d"; Spot >= 0.6 will parse it as "(a & b) -> (c & d)". - The random graph generator was fixed (again!) not to produce dead states as documented. - Locations in the error messages of the LTL parser were off by one.