scholarly journals Unresolved systems of language equations: Expressive power and decision problems

2005 ◽  
Vol 349 (3) ◽  
pp. 283-308 ◽  
Author(s):  
Alexander Okhotin
2017 ◽  
Vol 62 (4) ◽  
pp. 854-898 ◽  
Author(s):  
Dominik D. Freydenberger ◽  
Mario Holldack

2019 ◽  
Vol 798 ◽  
pp. 40-51
Author(s):  
Da-Jung Cho ◽  
Yo-Sub Han ◽  
Kai Salomaa ◽  
Taylor J. Smith

Author(s):  
Giuseppe De Giacomo ◽  
Antonio Di Stasio ◽  
Francesco Fuggitti ◽  
Sasha Rubin

We review PLTLf and PLDLf, the pure-past versions of the well-known logics on finite traces LTLf and LDLf, respectively. PLTLf and PLDLf are logics about the past, and so scan the trace backwards from the end towards the beginning. Because of this, we can exploit a foundational result on reverse languages to get an exponential improvement, over LTLf /LDLf , for computing the corresponding DFA. This exponential improvement is reflected in several forms of sequential decision making involving temporal specifications, such as planning and decision problems in non-deterministic and non-Markovian domains. Interestingly, PLTLf (resp., PLDLf ) has the same expressive power as LTLf (resp., LDLf ), but transforming a PLTLf (resp., PLDLf ) formula into its equivalent LTLf (resp.,LDLf) is quite expensive. Hence, to take advantage of the exponential improvement, properties of interest must be directly expressed in PLTLf /PLDLf .


2012 ◽  
Vol 416 ◽  
pp. 71-86 ◽  
Author(s):  
Alexander Okhotin ◽  
Oksana Yakimova

2010 ◽  
Vol 76 (3-4) ◽  
pp. 251-266 ◽  
Author(s):  
Alexander Okhotin

2007 ◽  
Vol 376 (1-2) ◽  
pp. 112-126 ◽  
Author(s):  
Alexander Okhotin ◽  
Oksana Yakimova

2005 ◽  
Vol 16 (05) ◽  
pp. 985-998 ◽  
Author(s):  
ALEXANDER OKHOTIN

Language equations with all Boolean operations and concatenation and a particular order on the set of solutions are proved to be equal in expressive power to the first-order Peano arithmetic. In particular, it is shown that the class of sets representable using k variables (for every k ≥ 2) is exactly the k-th level of the arithmetical hierarchy, i.e., the sets definable by recursive predicates with k alternating quantifiers. The property of having an extremal solution is shown to be nonrepresentable in first-order arithmetic.


Author(s):  
Nico Potyka

Bipolar abstract argumentation frameworks allow modeling decision problems by defining pro and contra arguments and their relationships. In some popular bipolar frameworks, there is an inherent tendency to favor either attack or support relationships. However, for some applications, it seems sensible to treat attack and support equally. Roughly speaking, turning an attack edge into a support edge, should just invert its meaning. We look at a recently introduced bipolar argumentation semantics and two novel alternatives and discuss their semantical and computational properties. Interestingly, the two novel semantics correspond to stable semantics if no support relations are present and maintain the computational complexity of stable semantics in general bipolar frameworks.


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