485,692 research outputs found
Implementation of Distributed Transactions in BPEL
Cílem této bakalářské práce je implementovat podporu distribuovaných transakcí do projektu RiftSaw tak, aby webové služby mohly být volány v rámci distribuovaných transakcí podnikovými procesy. A to pouze v tom případě, že operace webové služby vyžaduje být provedena v rámci distribuované transakce. Oproti již funkčním implementacím přináší podporu specifikace WS-BusinessActivity a jiný způsob kontroly, zda má podnikový proces použít distribuované transakce u volaných webových služeb.The goal of this work is to implement a support of distributed transactions into the project RiftSaw so that web services can be invoked within distributed transactions by business processes. And only if a web service operation requires to be performed within a distributed transaction. Comparing to already working implementations, the presented sulution brings support of WS-BusinessActivity specification and a different way of checking that a business process use distributed transactions for invoked web services.
Chainspace: A Sharded Smart Contracts Platform
Chainspace is a decentralized infrastructure, known as a distributed ledger,
that supports user defined smart contracts and executes user-supplied
transactions on their objects. The correct execution of smart contract
transactions is verifiable by all. The system is scalable, by sharding state
and the execution of transactions, and using S-BAC, a distributed commit
protocol, to guarantee consistency. Chainspace is secure against subsets of
nodes trying to compromise its integrity or availability properties through
Byzantine Fault Tolerance (BFT), and extremely high-auditability,
non-repudiation and `blockchain' techniques. Even when BFT fails, auditing
mechanisms are in place to trace malicious participants. We present the design,
rationale, and details of Chainspace; we argue through evaluating an
implementation of the system about its scaling and other features; we
illustrate a number of privacy-friendly smart contracts for smart metering,
polling and banking and measure their performance
Atomic Appends: Selling Cars and Coordinating Armies with Multiple Distributed Ledgers
The various applications using Distributed Ledger Technologies (DLT) or blockchains, have led to the introduction of a new "marketplace" where multiple types of digital assets may be exchanged. As each blockchain is designed to support specific types of assets and transactions, and no blockchain will prevail, the need to perform interblockchain transactions is already pressing.
In this work we examine the fundamental problem of interoperable and interconnected blockchains. In particular, we begin by introducing the Multi-Distributed Ledger Objects (MDLO), which is the result of aggregating multiple Distributed Ledger Objects - DLO (a DLO is a formalization of the blockchain) and that supports append and get operations of records (e.g., transactions) in them from multiple clients concurrently. Next we define the AtomicAppends problem, which emerges when the exchange of digital assets between multiple clients may involve appending records in more than one DLO. Specifically, AtomicAppend requires that either all records will be appended on the involved DLOs or none. We examine the solvability of this problem assuming rational and risk-averse clients that may fail by crashing, and under different client utility and append models, timing models, and client failure scenarios. We show that for some cases the existence of an intermediary is necessary for the problem solution. We propose the implementation of such intermediary over a specialized blockchain, we term Smart DLO (SDLO), and we show how this can be used to solve the AtomicAppends problem even in an asynchronous, client competitive environment, where all the clients may crash
Towards Efficient Abstractions for Concurrent Consensus
Consensus is an often occurring problem in concurrent and distributed
programming. We present a programming language with simple semantics and
build-in support for consensus in the form of communicating transactions. We
motivate the need for such a construct with a characteristic example of
generalized consensus which can be naturally encoded in our language. We then
focus on the challenges in achieving an implementation that can efficiently run
such programs. We setup an architecture to evaluate different implementation
alternatives and use it to experimentally evaluate runtime heuristics. This is
the basis for a research project on realistic programming language support for
consensus.Comment: 15 pages, 5 figures, symposium: TFP 201
DiLeNA: Distributed Ledger Network Analyzer
This paper describes the Distributed Ledger Network Analyzer (DiLeNA), a new
software tool for the analysis of the transactions network recorded in
Distributed Ledger Technologies (DLTs). The set of transactions in a DLT forms
a complex network. Studying its characteristics and peculiarities is of
paramount importance, in order to understand how users interact in the
distributed ledger system. The tool design and implementation is introduced and
some results are provided. In particular, the Bitcoin and Ethereum blockchains,
i.e. the most famous and used DLTs at the time of writing, have been analyzed
and compared.Comment: Proceeding of the 3rd Workshop on Cryptocurrencies and Blockchains
for Distributed Systems (CryBlock 2020
Distributed Basis Pursuit
We propose a distributed algorithm for solving the optimization problem Basis
Pursuit (BP). BP finds the least L1-norm solution of the underdetermined linear
system Ax = b and is used, for example, in compressed sensing for
reconstruction. Our algorithm solves BP on a distributed platform such as a
sensor network, and is designed to minimize the communication between nodes.
The algorithm only requires the network to be connected, has no notion of a
central processing node, and no node has access to the entire matrix A at any
time. We consider two scenarios in which either the columns or the rows of A
are distributed among the compute nodes. Our algorithm, named D-ADMM, is a
decentralized implementation of the alternating direction method of
multipliers. We show through numerical simulation that our algorithm requires
considerably less communications between the nodes than the state-of-the-art
algorithms.Comment: Preprint of the journal version of the paper; IEEE Transactions on
Signal Processing, Vol. 60, Issue 4, April, 201
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An Object-Based Approach to Implementing Distributed Concurrency Control
We have added distributed concurrency control to the MELD object system by representing in progress transactions as simulated objects. Transaction objects exploit MELD‘s normal message passing facilities to support the concurrency control mechanism. We have completed the implementation of an optimistic mechanism using transaction objects and have designed a two phase locking mechanism based on the same paradigm. We discuss the tradeoffs made and lessons learned, dealing both with transactions on objects and with transactions as objects
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