2,965 research outputs found
An automaton over data words that captures EMSO logic
We develop a general framework for the specification and implementation of
systems whose executions are words, or partial orders, over an infinite
alphabet. As a model of an implementation, we introduce class register
automata, a one-way automata model over words with multiple data values. Our
model combines register automata and class memory automata. It has natural
interpretations. In particular, it captures communicating automata with an
unbounded number of processes, whose semantics can be described as a set of
(dynamic) message sequence charts. On the specification side, we provide a
local existential monadic second-order logic that does not impose any
restriction on the number of variables. We study the realizability problem and
show that every formula from that logic can be effectively, and in elementary
time, translated into an equivalent class register automaton
A speculative execution approach to provide semantically aware contention management for concurrent systems
PhD ThesisMost modern platforms offer ample potention for parallel execution of concurrent programs yet concurrency control is required to exploit parallelism while maintaining program correctness. Pessimistic con-
currency control featuring blocking synchronization and mutual ex-
clusion, has given way to transactional memory, which allows the
composition of concurrent code in a manner more intuitive for the
application programmer. An important component in any transactional memory technique however is the policy for resolving conflicts
on shared data, commonly referred to as the contention management
policy.
In this thesis, a Universal Construction is described which provides
contention management for software transactional memory. The technique differs from existing approaches given that multiple execution
paths are explored speculatively and in parallel. In the resolution of
conflicts by state space exploration, we demonstrate that both concur-
rent conflicts and semantic conflicts can be solved, promoting multi-
threaded program progression.
We de ne a model of computation called Many Systems, which defines the execution of concurrent threads as a state space management
problem. An implementation is then presented based on concepts
from the model, and we extend the implementation to incorporate
nested transactions. Results are provided which compare the performance of our approach with an established contention management
policy, under varying degrees of concurrent and semantic conflicts. Finally, we provide performance results from a number of search strategies, when nested transactions are introduced
ARPA Whitepaper
We propose a secure computation solution for blockchain networks. The
correctness of computation is verifiable even under malicious majority
condition using information-theoretic Message Authentication Code (MAC), and
the privacy is preserved using Secret-Sharing. With state-of-the-art multiparty
computation protocol and a layer2 solution, our privacy-preserving computation
guarantees data security on blockchain, cryptographically, while reducing the
heavy-lifting computation job to a few nodes. This breakthrough has several
implications on the future of decentralized networks. First, secure computation
can be used to support Private Smart Contracts, where consensus is reached
without exposing the information in the public contract. Second, it enables
data to be shared and used in trustless network, without disclosing the raw
data during data-at-use, where data ownership and data usage is safely
separated. Last but not least, computation and verification processes are
separated, which can be perceived as computational sharding, this effectively
makes the transaction processing speed linear to the number of participating
nodes. Our objective is to deploy our secure computation network as an layer2
solution to any blockchain system. Smart Contracts\cite{smartcontract} will be
used as bridge to link the blockchain and computation networks. Additionally,
they will be used as verifier to ensure that outsourced computation is
completed correctly. In order to achieve this, we first develop a general MPC
network with advanced features, such as: 1) Secure Computation, 2) Off-chain
Computation, 3) Verifiable Computation, and 4)Support dApps' needs like
privacy-preserving data exchange
Competition at the Left Edge: Left-Dislocation vs. Topicalization in Heritage Germanic
The present work analyses left dislocation (LD) in Heritage German and Heritage Norwegian as a phenomenon of the left periphery of the clause. Fieldwork conducted from the 1940s through the 2010s shows both a robust maintenance of verb second (V2) and that pragmatically-conditioned copy left dislocation (CLD) occurs in complementary distribution with V2 in these heritage languages (HLs), and in ways that are consistent with the pre-immigration, homeland varieties. This study therefore unifies CLD and bare topic constructions (BTCs) under a single structure, in which the resumptive pronoun is either overt (CLD) or covert (BTC), with CLD being restricted to instances where there is either a pragmatic condition (e.g., emphasis, contrast, topic shift) or an interlocutor (e.g., narration). Infrequently, some speakers employ CLD in the absence of these conditions, where BTC would otherwise be expected. The authors propose that this change is motivated diachronically as the reanalysis of specifiers as heads, under the Avoid Silent Heads (ASH) principle (Eide 2011; cf. van Gelderen 2007), and consistent with the tendency for (heritage) speakers to prefer overt heads to covert ones (Polinsky 2018). Such change corresponds with the lexicalization of formerly pragmatically-conditioned XPs as obligatory heads.publishedVersio
Specifications and programs for computer software validation
Three software products developed during the study are reported and include: (1) FORTRAN Automatic Code Evaluation System, (2) the Specification Language System, and (3) the Array Index Validation System
Safe Programming Over Distributed Streams
The sheer scale of today\u27s data processing needs has led to a new paradigm of software systems centered around requirements for high-throughput, distributed, low-latency computation.Despite their widespread adoption, existing solutions have yet to provide a programming model with safe semantics -- and they disagree on basic design choices, in particular with their approach to parallelism. As a result, naive programmers are easily led to introduce correctness and performance bugs.
This work proposes a reliable programming model for modern distributed stream processing, founded in a type system for partially ordered data streams. On top of the core type system, we propose language abstractions for working with streams -- mechanisms to build stream operators with (1) type-safe compositionality, (2) deterministic distribution, (3) run-time testing, and (4) static performance bounds. Our thesis is that viewing streams as partially ordered conveniently exposes parallelism without compromising safety or determinism. The ideas contained in this work are implemented in a series of open source software projects, including the Flumina, DiffStream, and Data Transducers libraries
On Split-State Quantum Tamper Detection and Non-Malleability
Tamper-detection codes (TDCs) and non-malleable codes (NMCs) are now
fundamental objects at the intersection of cryptography and coding theory. Both
of these primitives represent natural relaxations of error-correcting codes and
offer related security guarantees in adversarial settings where error
correction is impossible. While in a TDC, the decoder is tasked with either
recovering the original message or rejecting it, in an NMC, the decoder is
additionally allowed to output a completely unrelated message.
In this work, we study quantum analogs of one of the most well-studied
adversarial tampering models: the so-called split-state tampering model. In the
-split-state model, the codeword (or code-state) is divided into shares,
and each share is tampered with "locally". Previous research has primarily
focused on settings where the adversaries' local quantum operations are
assisted by an unbounded amount of pre-shared entanglement, while the code
remains unentangled, either classical or separable.
We construct quantum TDCs and NMCs in several
analogs of the split-state model, which are provably impossible using just
classical codes. In particular, against split-state adversaries restricted to
local (unentangled) operations, local operations and classical communication,
as well as a "bounded storage model" where they are limited to a finite amount
of pre-shared entanglement. We complement our code constructions in two
directions. First, we present applications to designing secret sharing schemes,
which inherit similar non-malleable and tamper-detection guarantees. Second, we
discuss connections between our codes and quantum encryption schemes, which we
leverage to prove singleton-type bounds on the capacity of certain families of
quantum NMCs in the split-state model
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