821 research outputs found
Representing a P-complete problem by small trellis automata
A restricted case of the Circuit Value Problem known as the Sequential NOR
Circuit Value Problem was recently used to obtain very succinct examples of
conjunctive grammars, Boolean grammars and language equations representing
P-complete languages (Okhotin, http://dx.doi.org/10.1007/978-3-540-74593-8_23
"A simple P-complete problem and its representations by language equations",
MCU 2007). In this paper, a new encoding of the same problem is proposed, and a
trellis automaton (one-way real-time cellular automaton) with 11 states solving
this problem is constructed
A Modal Logic for Termgraph Rewriting
We propose a modal logic tailored to describe graph transformations and
discuss some of its properties. We focus on a particular class of graphs called
termgraphs. They are first-order terms augmented with sharing and cycles.
Termgraphs allow one to describe classical data-structures (possibly with
pointers) such as doubly-linked lists, circular lists etc. We show how the
proposed logic can faithfully describe (i) termgraphs as well as (ii) the
application of a termgraph rewrite rule (i.e. matching and replacement) and
(iii) the computation of normal forms with respect to a given rewrite system.
We also show how the proposed logic, which is more expressive than
propositional dynamic logic, can be used to specify shapes of classical
data-structures (e.g. binary trees, circular lists etc.)
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