1,457 research outputs found
Blazes: Coordination Analysis for Distributed Programs
Distributed consistency is perhaps the most discussed topic in distributed
systems today. Coordination protocols can ensure consistency, but in practice
they cause undesirable performance unless used judiciously. Scalable
distributed architectures avoid coordination whenever possible, but
under-coordinated systems can exhibit behavioral anomalies under fault, which
are often extremely difficult to debug. This raises significant challenges for
distributed system architects and developers. In this paper we present Blazes,
a cross-platform program analysis framework that (a) identifies program
locations that require coordination to ensure consistent executions, and (b)
automatically synthesizes application-specific coordination code that can
significantly outperform general-purpose techniques. We present two case
studies, one using annotated programs in the Twitter Storm system, and another
using the Bloom declarative language.Comment: Updated to include additional materials from the original technical
report: derivation rules, output stream label
Relational transducers for declarative networking
Motivated by a recent conjecture concerning the expressiveness of declarative
networking, we propose a formal computation model for "eventually consistent"
distributed querying, based on relational transducers. A tight link has been
conjectured between coordination-freeness of computations, and monotonicity of
the queries expressed by such computations. Indeed, we propose a formal
definition of coordination-freeness and confirm that the class of monotone
queries is captured by coordination-free transducer networks.
Coordination-freeness is a semantic property, but the syntactic class that we
define of "oblivious" transducers also captures the same class of monotone
queries. Transducer networks that are not coordination-free are much more
powerful
Optimal Broadcasting Strategies for Conjunctive Queries over Distributed Data
In a distributed context where data is dispersed over many computing nodes, monotone queries can be evaluated in an eventually consistent and coordination-free manner through a simple but naive broadcasting strategy which makes all data available on every computing node. In this paper, we investigate more economical broadcasting strategies for full conjunctive queries without self-joins that only transmit a part of the local data necessary to evaluate the query at hand. We consider oblivious broadcasting strategies which determine which local facts to broadcast independent of the data at other computing nodes. We introduce the notion of broadcast dependency set (BDS) as a sound and complete formalism to represent locally optimal oblivious broadcasting functions. We provide algorithms to construct a BDS for a given conjunctive query and study the complexity of various decision problems related to these algorithms
Datalog Queries Distributing over Components
We investigate the class D of queries that distribute over components. These are the queries that can be evaluated by taking the union of the query results over the connected components of the database instance. We show that it is undecidable whether a (positive) Datalog program distributes over components. Additionally, we show that connected Datalog ¬ (the fragment of Datalog ¬ where all rules are connected) provides an effective syntax for Datalog ¬ programs that distribute over components under the stratified as well as under the well-founded semantics. As a corollary, we obtain a simple proof for one of the main results in previous work [19], namely, that the classic win-move query is in F2 (a particular class of coordination-free queries)
THE CHANGING TYPES OF SOCIAL SURVEILLANCE THROUGH GLOBALIZATION
Each individual takes part in social surveillance both as the watcher and the watched. The degree of watching and being watched, however, shows a substantial change as the world becomes more globalized. There are three main types of social surveillance, based on whether the space that is being watched is somewhere local, global or a cyberspace. The first type of surveillance is considered a Panopticon emerged with modernism, where a small group of people watches over a larger group of people. The second one is the Synopticon where the many watch over the few. Emerged especially with the growth of the mass media, the Synopticon is the product of a more globalized world when compared to the concept of Panopticon. The third type of surveillance is the Omnipticon, where both Panopticon and Synopticon are applied simultaneously. While the globalization has stripped a minority of the privilege of watching and conferred it on the whole of society, surveillance has gradually begun to evolve from a mean of psychological pressure into an alluring psychological desire. As the world becomes more globalized, the grip of social control becomes firmer and stronger than thought even though the physical local pressures on the individual seem to have been diminished. While it might seem liberating at first sight, the globalization also leads to an anti-emancipatory world. 
Datalog Unchained
International audienceThis is the companion paper of a talk in the Gems of PODS series, that reviews the development, starting at PODS 1988, of a family of Datalog-like languages with procedural, forward chaining semantics, providing an alternative to the classical declarative, model-theoretic semantics. These languages also provide a unified formalism that can express important classes of queries including fixpoint, while, and all computable queries. They can also incorporate in a natural fashion updates and nondeterminism. Datalog variants with forward chaining semantics have been adopted in a variety of settings, including active databases, production systems, distributed data exchange, and data-driven reactive systems
Segment Routing: a Comprehensive Survey of Research Activities, Standardization Efforts and Implementation Results
Fixed and mobile telecom operators, enterprise network operators and cloud
providers strive to face the challenging demands coming from the evolution of
IP networks (e.g. huge bandwidth requirements, integration of billions of
devices and millions of services in the cloud). Proposed in the early 2010s,
Segment Routing (SR) architecture helps face these challenging demands, and it
is currently being adopted and deployed. SR architecture is based on the
concept of source routing and has interesting scalability properties, as it
dramatically reduces the amount of state information to be configured in the
core nodes to support complex services. SR architecture was first implemented
with the MPLS dataplane and then, quite recently, with the IPv6 dataplane
(SRv6). IPv6 SR architecture (SRv6) has been extended from the simple steering
of packets across nodes to a general network programming approach, making it
very suitable for use cases such as Service Function Chaining and Network
Function Virtualization. In this paper we present a tutorial and a
comprehensive survey on SR technology, analyzing standardization efforts,
patents, research activities and implementation results. We start with an
introduction on the motivations for Segment Routing and an overview of its
evolution and standardization. Then, we provide a tutorial on Segment Routing
technology, with a focus on the novel SRv6 solution. We discuss the
standardization efforts and the patents providing details on the most important
documents and mentioning other ongoing activities. We then thoroughly analyze
research activities according to a taxonomy. We have identified 8 main
categories during our analysis of the current state of play: Monitoring,
Traffic Engineering, Failure Recovery, Centrally Controlled Architectures, Path
Encoding, Network Programming, Performance Evaluation and Miscellaneous...Comment: SUBMITTED TO IEEE COMMUNICATIONS SURVEYS & TUTORIAL
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