2,793 research outputs found
Discovering Restricted Regular Expressions with Interleaving
Discovering a concise schema from given XML documents is an important problem
in XML applications. In this paper, we focus on the problem of learning an
unordered schema from a given set of XML examples, which is actually a problem
of learning a restricted regular expression with interleaving using positive
example strings. Schemas with interleaving could present meaningful knowledge
that cannot be disclosed by previous inference techniques. Moreover, inference
of the minimal schema with interleaving is challenging. The problem of finding
a minimal schema with interleaving is shown to be NP-hard. Therefore, we
develop an approximation algorithm and a heuristic solution to tackle the
problem using techniques different from known inference algorithms. We do
experiments on real-world data sets to demonstrate the effectiveness of our
approaches. Our heuristic algorithm is shown to produce results that are very
close to optimal.Comment: 12 page
Expressiveness modulo Bisimilarity of Regular Expressions with Parallel Composition (Extended Abstract)
The languages accepted by finite automata are precisely the languages denoted
by regular expressions. In contrast, finite automata may exhibit behaviours
that cannot be described by regular expressions up to bisimilarity. In this
paper, we consider extensions of the theory of regular expressions with various
forms of parallel composition and study the effect on expressiveness. First we
prove that adding pure interleaving to the theory of regular expressions
strictly increases its expressiveness up to bisimilarity. Then, we prove that
replacing the operation for pure interleaving by ACP-style parallel composition
gives a further increase in expressiveness. Finally, we prove that the theory
of regular expressions with ACP-style parallel composition and encapsulation is
expressive enough to express all finite automata up to bisimilarity. Our
results extend the expressiveness results obtained by Bergstra, Bethke and
Ponse for process algebras with (the binary variant of) Kleene's star
operation.Comment: In Proceedings EXPRESS'10, arXiv:1011.601
A thread calculus with molecular dynamics
We present a theory of threads, interleaving of threads, and interaction
between threads and services with features of molecular dynamics, a model of
computation that bears on computations in which dynamic data structures are
involved. Threads can interact with services of which the states consist of
structured data objects and computations take place by means of actions which
may change the structure of the data objects. The features introduced include
restriction of the scope of names used in threads to refer to data objects.
Because that feature makes it troublesome to provide a model based on
structural operational semantics and bisimulation, we construct a projective
limit model for the theory.Comment: 47 pages; examples and results added, phrasing improved, references
replace
Iterative Multiuser Detection and Decoding with Spatially Coupled Interleaving
Spatially coupled (SC) interleaving is proposed to improve the performance of
iterative multiuser detection and decoding (MUDD) for quasi-static fading
multiple-input multiple-output systems. The linear minimum mean-squared error
(LMMSE) demodulator is used to reduce the complexity and to avoid error
propagation. Furthermore, sliding window MUDD is proposed to circumvent an
increase of the decoding latency due to SC interleaving. Theoretical and
numerical analyses show that SC interleaving can improve the performance of the
iterative LMMSE MUDD for regular low-density parity-check codes.Comment: Long version of a paper submitted to IEEE Wireless Commun. Let
From Finite Automata to Regular Expressions and Back--A Summary on Descriptional Complexity
The equivalence of finite automata and regular expressions dates back to the
seminal paper of Kleene on events in nerve nets and finite automata from 1956.
In the present paper we tour a fragment of the literature and summarize results
on upper and lower bounds on the conversion of finite automata to regular
expressions and vice versa. We also briefly recall the known bounds for the
removal of spontaneous transitions (epsilon-transitions) on non-epsilon-free
nondeterministic devices. Moreover, we report on recent results on the average
case descriptional complexity bounds for the conversion of regular expressions
to finite automata and brand new developments on the state elimination
algorithm that converts finite automata to regular expressions.Comment: In Proceedings AFL 2014, arXiv:1405.527
Static Analysis of Run-Time Errors in Embedded Real-Time Parallel C Programs
We present a static analysis by Abstract Interpretation to check for run-time
errors in parallel and multi-threaded C programs. Following our work on
Astr\'ee, we focus on embedded critical programs without recursion nor dynamic
memory allocation, but extend the analysis to a static set of threads
communicating implicitly through a shared memory and explicitly using a finite
set of mutual exclusion locks, and scheduled according to a real-time
scheduling policy and fixed priorities. Our method is thread-modular. It is
based on a slightly modified non-parallel analysis that, when analyzing a
thread, applies and enriches an abstract set of thread interferences. An
iterator then re-analyzes each thread in turn until interferences stabilize. We
prove the soundness of our method with respect to the sequential consistency
semantics, but also with respect to a reasonable weakly consistent memory
semantics. We also show how to take into account mutual exclusion and thread
priorities through a partitioning over an abstraction of the scheduler state.
We present preliminary experimental results analyzing an industrial program
with our prototype, Th\'es\'ee, and demonstrate the scalability of our
approach
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