30,047 research outputs found
Protocols for Integrity Constraint Checking in Federated Databases
A federated database is comprised of multiple interconnected database systems that primarily operate independently but cooperate to a certain extent. Global integrity constraints can be very useful in federated databases, but the lack of global queries, global transaction mechanisms, and global concurrency control renders traditional constraint management techniques inapplicable. This paper presents a threefold contribution to integrity constraint checking in federated databases: (1) The problem of constraint checking in a federated database environment is clearly formulated. (2) A family of protocols for constraint checking is presented. (3) The differences across protocols in the family are analyzed with respect to system requirements, properties guaranteed by the protocols, and processing and communication costs. Thus, our work yields a suite of options from which a protocol can be chosen to suit the system capabilities and integrity requirements of a particular federated database environment
Integrity Constraint Checking in Federated Databases
A federated database is comprised of multiple interconnected databases that cooperate in an autonomous fashion. Global integrity constraints are very useful in federated databases, but the lack of global queries, global transaction mechanisms, and global concurrency control renders traditional constraint management techniques inapplicable. The paper presents a threefold contribution to integrity constraint checking in federated databases: (1) the problem of constraint checking in a federated database environment is clearly formulated; (2) a family of cooperative protocols for constraint checking is presented; (3) the differences across protocols in the family are analyzed with respect to system requirements, properties guaranteed, and costs involved. Thus, we provide a suite of options with protocols for various environments with specific system capabilities and integrity requirement
A Fault Tolerant, Dynamic and Low Latency BDII Architecture for Grids
The current BDII model relies on information gathering from agents that run
on each core node of a Grid. This information is then published into a Grid
wide information resource known as Top BDII. The Top level BDIIs are updated
typically in cycles of a few minutes each. A new BDDI architecture is proposed
and described in this paper based on the hypothesis that only a few attribute
values change in each BDDI information cycle and consequently it may not be
necessary to update each parameter in a cycle. It has been demonstrated that
significant performance gains can be achieved by exchanging only the
information about records that changed during a cycle. Our investigations have
led us to implement a low latency and fault tolerant BDII system that involves
only minimal data transfer and facilitates secure transactions in a Grid
environment.Comment: 18 pages; 10 figures; 4 table
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
Developing a distributed electronic health-record store for India
The DIGHT project is addressing the problem of building a scalable and highly available information store for the Electronic Health Records (EHRs) of the over one billion citizens of India
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