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A new algorithm is presented for the D0L sequence equivalence problem which, when the alphabets are fixed, works in time polynomial in the rest of the input data. The algorithm uses a polynomial encoding of words and certain well-known properties of -rational sequences.
A new algorithm is presented for the D0L sequence equivalence problem which, when the alphabets are fixed, works in time polynomial in the rest of the input data. The algorithm uses a polynomial encoding of words and certain well-known properties of -rational sequences.
We explore the borderline between decidability and
undecidability of the following question: “Let C be a
class of codes. Given a machine of type X, is it decidable
whether the language lies in C or not?” for
codes in general, ω-codes, codes of finite and bounded
deciphering delay, prefix, suffix and bi(pre)fix codes, and for
finite automata equipped with different versions of push-down stores
and counters.
In this paper we prove the decidability of the HD0L ultimate periodicity problem.
Various static analyses of functional programming languages
that permit infinite data structures make use of set
constants like Top, Inf, and Bot, denoting
all terms, all lists not eventually ending in Nil, and
all non-terminating programs, respectively. We use a set
language that permits union, constructors and recursive
definition of set constants with a greatest fixpoint semantics
in the set of all, also infinite, computable trees,
where all term constructors are non-strict.
This...
In the last decade, formal methods have proved their interest when analyzing security protocols. Security protocols require in particular to reason about the attacker knowledge. Two standard notions are often considered in formal approaches: deducibility and indistinguishability relations. The first notion states whether an attacker can learn the value of a secret, while the latter states whether an attacker can notice some difference between protocol runs with different values of the secret. Several...
In the last decade, formal methods have proved their interest when
analyzing security protocols. Security protocols require in
particular to reason about the attacker knowledge. Two standard
notions are often considered in formal approaches: deducibility and
indistinguishability relations. The first notion states whether an
attacker can learn the value of a secret, while the latter states
whether an attacker can notice some difference between protocol runs
with different values of the secret. Several...
We consider logics on
and which are weaker than
Presburger arithmetic and
we settle the following decision
problem: given a k-ary
relation on and
which are first order definable in
Presburger arithmetic, are they definable in these
weaker logics? These logics, intuitively,
are obtained by considering modulo and threshold counting predicates for differences of two variables.
We consider the four families of recognizable, synchronous,
deterministic rational and rational subsets of a direct product
of free monoids.
They form a strict hierarchy and we investigate the following
decision problem: given a relation in one of the families,
does it belong to a smaller family?
We settle the problem entirely when all monoids have a unique
generator and fill some gaps in the general case.
In particular, adapting a proof of Stearns, we show that it is recursively decidable
whether...
In this paper we argue that for fuzzy unification we need a procedural and declarative semantics (as opposed to the two valued case, where declarative semantics is hidden in the requirement that unified terms are syntactically – letter by letter – identical). We present an extension of the syntactic model of unification to allow near matches, defined using a similarity relation. We work in Hájek’s fuzzy logic in narrow sense. We base our semantics on a formal model of fuzzy logic programming extended...
We consider the defect theorem in the context of labelled
polyominoes, i.e., two-dimensional figures. The classical version of
this property states that if a set of n words is not a code then
the words can be expressed as a product of at most n - 1 words, the
smaller set being a code. We survey several two-dimensional
extensions exhibiting the boundaries where the theorem fails. In
particular, we establish the defect property in the case of three
dominoes (n × 1 or 1 × n rectangles).
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