2,122 research outputs found
Parallel Time and Quantifier Prfixes
We characterize the amount of alternation between blocks of digital quantiļ¬ers (having both existential and universal), blocks of real existential quantiļ¬ers, and blocks of real universal quantiļ¬ers that can be decided in parallel polynomial time over the reals. We do so under the assumption that blocks have a uniform bound in their size, both for the case of this bound to be polynomial and constant. As a result of this characterization (and as a stepping stone towards it) we prove a real version of Savitch Theorem
Crossing the Border Historical and Linguistic Divides Among the Bunaq in Central Timor
The Bunaq are a Papuan language-speaking people straddling the border of Indonesian West Timor and independent East Timor. This paper looks at the history of the Bunaq as a āborderā people in Timor. āBorderā is interpreted here in two ways, as referring to: (i) a political division, the boundary line separating one country from another, and (ii) a linguistic division, the distinguishing line between Papuan and Austronesian languages. I examine the effect that the Bunaq position at the political and linguistic borders of Timor has had on the people and their language
Presenting and predicating lower events
The effects of different forms of predication have been insightfully (and almost exclusively) studied for 'simple' cases of predication, of which the 'presentational sentence' is maybe the paradigm instantiation. It is the aim of this paper to show that thc same kind of effects as well as in fact the same kind of structures are present at embedded levels in thematically and otherwise more complex structures. Beyond presentational sentences, 'unaccusative' experiencing constructions involving a dative subject, 'double object constructions' and - to a lesser extent - spraylload constructions are discussed. For all of these, it is argued that they comprise a predication encoding the ascription of a transient temporal property to a location. On this basis, a proposal is made as to how the scope asymmetry between the two arguments involved in the colistructions can be explained. Furthermore, a proposal is made as to how what has been called 'argument shift' is motivated
A Fine-Grained Hierarchy of Hard Problems in the Separated Fragment
Recently, the separated fragment (SF) has been introduced and proved to be
decidable. Its defining principle is that universally and existentially
quantified variables may not occur together in atoms. The known upper bound on
the time required to decide SF's satisfiability problem is formulated in terms
of quantifier alternations: Given an SF sentence
in which is quantifier free, satisfiability can be decided in
nondeterministic -fold exponential time. In the present paper, we conduct a
more fine-grained analysis of the complexity of SF-satisfiability. We derive an
upper and a lower bound in terms of the degree of interaction of existential
variables (short: degree)}---a novel measure of how many separate existential
quantifier blocks in a sentence are connected via joint occurrences of
variables in atoms. Our main result is the -NEXPTIME-completeness of the
satisfiability problem for the set of all SF sentences that have
degree or smaller. Consequently, we show that SF-satisfiability is
non-elementary in general, since SF is defined without restrictions on the
degree. Beyond trivial lower bounds, nothing has been known about the hardness
of SF-satisfiability so far.Comment: Full version of the LICS 2017 extended abstract having the same
title, 38 page
Logical and deep learning methods for temporal reasoning
In this thesis, we study logical and deep learning methods for the temporal reasoning of reactive systems. In Part I, we determine decidability borders for the satisfiability and realizability problem of temporal hyperproperties. Temporal hyperproperties relate multiple computation traces to each other and are expressed in a temporal hyperlogic. In particular, we identify decidable fragments of the highly expressive hyperlogics HyperQPTL and HyperCTL*. As an application, we elaborate on an enforcement mechanism for temporal hyperproperties. We study explicit enforcement algorithms for specifications given as formulas in universally quantified HyperLTL. In Part II, we train a (deep) neural network on the trace generation and realizability problem of linear-time temporal logic (LTL). We consider a method to generate large amounts of additional training data from practical specification patterns. The training data is generated with classical solvers, which provide one of many possible solutions to each formula. We demonstrate that it is sufficient to train on those particular solutions such that the neural network generalizes to the semantics of the logic. The neural network can predict solutions even for formulas from benchmarks from the literature on which the classical solver timed out. Additionally, we show that it solves a significant portion of problems from the annual synthesis competition (SYNTCOMP) and even out-of-distribution examples from a recent case study.Diese Arbeit befasst sich mit logischen Methoden und mehrschichtigen Lernmethoden fĆ¼r das zeitabhƤngige Argumentieren Ć¼ber reaktive Systeme. In Teil I werden die Grenzen der Entscheidbarkeit des ErfĆ¼llbarkeits- und des Realisierbarkeitsproblem von temporalen Hypereigenschaften bestimmt. Temporale Hypereigenschaften setzen mehrere Berechnungsspuren zueinander in Beziehung und werden in einer temporalen Hyperlogik ausgedrĆ¼ckt. Insbesondere werden entscheidbare Fragmente der hochexpressiven Hyperlogiken HyperQPTL und HyperCTL* identifiziert. Als Anwendung wird ein Enforcement-Mechanismus fĆ¼r temporale Hypereigenschaften erarbeitet. Explizite Enforcement-Algorithmen fĆ¼r Spezifikationen, die als Formeln in universell quantifiziertem HyperLTL angegeben werden, werden untersucht. In Teil II wird ein (mehrschichtiges) neuronales Netz auf den Problemen der Spurgenerierung und Realisierbarkeit von Linear-zeit Temporallogik (LTL) trainiert. Es wird eine Methode betrachtet, um aus praktischen Spezifikationsmustern groĆe Mengen zusƤtzlicher Trainingsdaten zu generieren. Die Trainingsdaten werden mit klassischen Solvern generiert, die zu jeder Formel nur eine von vielen mƶglichen Lƶsungen liefern. Es wird gezeigt, dass es ausreichend ist, an diesen speziellen Lƶsungen zu trainieren, sodass das neuronale Netz zur Semantik der Logik generalisiert. Das neuronale Netz kann Lƶsungen sogar fĆ¼r Formeln aus Benchmarks aus der Literatur vorhersagen, bei denen der klassische Solver eine ZeitĆ¼berschreitung hatte. ZusƤtzlich wird gezeigt, dass das neuronale Netz einen erheblichen Teil der Probleme aus dem jƤhrlichen Synthesewettbewerb (SYNTCOMP) und sogar Beispiele auĆerhalb der Distribution aus einer aktuellen Fallstudie lƶsen kann
Analyzing Conflict Freedom For Multi-threaded Programs With Time Annotations
Avoiding access conflicts is a major challenge in the design of
multi-threaded programs. In the context of real-time systems, the absence of
conflicts can be guaranteed by ensuring that no two potentially conflicting
accesses are ever scheduled concurrently.In this paper, we analyze programs
that carry time annotations specifying the time for executing each statement.
We propose a technique for verifying that a multi-threaded program with time
annotations is free of access conflicts. In particular, we generate constraints
that reflect the possible schedules for executing the program and the required
properties. We then invoke an SMT solver in order to verify that no execution
gives rise to concurrent conflicting accesses. Otherwise, we obtain a trace
that exhibits the access conflict.Comment: http://journal.ub.tu-berlin.de/eceasst/article/view/97
Graphical Verification of a Spatial Logic for the Graphical Verification of a Spatial Logic for the pi-calculus
The paper introduces a novel approach to the verification of spatial properties for finite [pi]-calculus specifications. The mechanism is based on a recently proposed graphical encoding for mobile calculi: Each process is mapped into a (ranked) graph, such that the denotation is fully abstract with respect to the usual structural congruence (i.e., two processes are equivalent exactly when the corresponding encodings yield the same graph). Spatial properties for reasoning about the behavior and the structure of pi-calculus processes are then expressed in a logic introduced by Caires, and they are verified on the graphical encoding of a process, rather than on its textual representation. More precisely, the graphical presentation allows for providing a simple and easy to implement verification algorithm based on the graphical encoding (returning true if and only if a given process verifies a given spatial formula)
Computational Arithmetic Geometry I: Sentences Nearly in the Polynomial Hierarchy
We consider the average-case complexity of some otherwise undecidable or open
Diophantine problems. More precisely, consider the following: (I) Given a
polynomial f in Z[v,x,y], decide the sentence \exists v \forall x \exists y
f(v,x,y)=0, with all three quantifiers ranging over N (or Z). (II) Given
polynomials f_1,...,f_m in Z[x_1,...,x_n] with m>=n, decide if there is a
rational solution to f_1=...=f_m=0. We show that, for almost all inputs,
problem (I) can be done within coNP. The decidability of problem (I), over N
and Z, was previously unknown. We also show that the Generalized Riemann
Hypothesis (GRH) implies that, for almost all inputs, problem (II) can be done
via within the complexity class PP^{NP^NP}, i.e., within the third level of the
polynomial hierarchy. The decidability of problem (II), even in the case m=n=2,
remains open in general.
Along the way, we prove results relating polynomial system solving over C, Q,
and Z/pZ. We also prove a result on Galois groups associated to sparse
polynomial systems which may be of independent interest. A practical
observation is that the aforementioned Diophantine problems should perhaps be
avoided in the construction of crypto-systems.Comment: Slight revision of final journal version of an extended abstract
which appeared in STOC 1999. This version includes significant corrections
and improvements to various asymptotic bounds. Needs cjour.cls to compil
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