284 research outputs found
Managing Uncertain Complex Events in Web of Things Applications
A critical issue in the Web of Things (WoT) is the need to process and analyze the interactions of Web-interconnected real-world
objects. Complex Event Processing (CEP) is a powerful technology for analyzing streams of information about real-time distributed events, coming from different sources, and for extracting conclusions from them. However, in many situations these events are not free from uncertainty, due to either unreliable data sources and networks, measurement uncertainty, or to the inability to determine whether an event has actually happened or not. This short research paper discusses how CEP systems
can incorporate different kinds of uncertainty, both in the events and in the rules. A case study is used to validate the proposal, and we discuss the benefits and limitations of this CEP extension.Universidad de Málaga. Campus de Excelencia Internacional AndalucĂa Tech
On Context-Aware Publish-Subscribe
Complex communication patterns often need to take into account the characteristics of the environment, or the situation, in which the information to be communicated is produced or consumed. Publish-subscribe, and particularly its content-based incarnation, is often used to convey this information by encoding the “context ” of the publisher into the published messages, taking advantage of the expressiveness of content-based addressing to encode context-aware communication patterns. In this paper we claim that this approach is both inadequate and inefficient and propose a context-aware publish-subscribe model of communication as a better alternative. In particular, we describe the API of a new publish-subscribe model that is both content and context-based, and we explore possible routing schemas to implement this new model in a distributed publish-subscribe system potentially improving traditional content-based routing
DSOL: a declarative approach to self-adaptive service orchestrations
Service oriented computing (SOC) has brought a simplification in the way distributed applications can be built. Mainstream approaches, however, failed to support dynamic, self-managed compositions that would empower even non-technical users to build their own orchestrations. Indeed, because of the changeable world in which they are embedded, service compositions must be able to adapt to changes that may happen at run-time. Unfortunately, mainstream SOC languages, like BPEL and BPMN, make it quite hard to develop such kind of self-adapting orchestrations. We claim that this is mostly due to the imperative programming paradigm they are based on. To overcome this limitation we propose a radically different, strongly declarative approach to model service orchestration, which is easier to use and results in more flexible and self-adapting orchestrations. An ad-hoc engine, leveraging well-known planning techniques, interprets such models to support dynamic service orchestration at run-time
Trace checking of Metric Temporal Logic with Aggregating Modalities using MapReduce
Modern complex software systems produce a large amount of execution data,
often stored in logs. These logs can be analyzed using trace checking
techniques to check whether the system complies with its requirements
specifications. Often these specifications express quantitative properties of
the system, which include timing constraints as well as higher-level
constraints on the occurrences of significant events, expressed using aggregate
operators. In this paper we present an algorithm that exploits the MapReduce
programming model to check specifications expressed in a metric temporal logic
with aggregating modalities, over large execution traces. The algorithm
exploits the structure of the formula to parallelize the evaluation, with a
significant gain in time. We report on the assessment of the implementation -
based on the Hadoop framework - of the proposed algorithm and comment on its
scalability.Comment: 16 pages, 6 figures, Extended version of the SEFM 2014 pape
AIOCJ: A Choreographic Framework for Safe Adaptive Distributed Applications
We present AIOCJ, a framework for programming distributed adaptive
applications. Applications are programmed using AIOC, a choreographic language
suited for expressing patterns of interaction from a global point of view. AIOC
allows the programmer to specify which parts of the application can be adapted.
Adaptation takes place at runtime by means of rules, which can change during
the execution to tackle possibly unforeseen adaptation needs. AIOCJ relies on a
solid theory that ensures applications to be deadlock-free by construction also
after adaptation. We describe the architecture of AIOCJ, the design of the AIOC
language, and an empirical validation of the framework.Comment: Technical Repor
Orbital angular momentum multiplication in plasmonic vortex cavities
Orbital angular momentum of light is a core feature in photonics. Its
confinement to surfaces using plasmonics has unlocked many phenomena and
potential applications. Here we introduce the reflection from structural
boundaries as a new degree of freedom to generate and control plasmonic orbital
angular momentum. We experimentally demonstrate plasmonic vortex cavities,
generating a succession of vortex pulses with increasing topological charge as
a function of time. We track the spatio-temporal dynamics of these angularly
decelerating plasmon pulse train within the cavities for over 300 femtoseconds
using time-resolved Photoemission Electron Microscopy, showing that the angular
momentum grows by multiples of the chiral order of the cavity. The introduction
of this degree of freedom to tame orbital angular momentum delivered by
plasmonic vortices, could miniaturize pump-probe-like quantum initialization
schemes, increase the torque exerted by plasmonic tweezers and potentially
achieve vortex lattice cavities with dynamically evolving topology
Active Coordination in Ad Hoc Networks
Abstract. The increasing ubiquity of communicating mobile devices and vastly different mobile application needs have led to the emergence of middleware models for ad hoc networks that simplify application pro-gramming. One such system, EgoSpaces, addresses specific needs of indi-vidual applications, allowing them to define what data is included in their operating context using declarative specifications constraining properties of data, agents that own the data, hosts on which those agents are run-ning, and attributes of the ad hoc network. In the resulting coordination model, application agents interact with a dynamically changing environ-ment through a set of views, or custom defined projections of the set of data present in the surrounding ad hoc network. This paper builds on EgoSpaces by allowing agents to assign behaviors to their personal-ized views. Behaviors consist of actions that are automatically performed in response to specified changes in a view. Behaviors discussed in this paper encompass reactive programming, transparent data migration, au-tomatic data duplication, and event capture. Formal semantic definitions and programming examples are given for each behavior.
High-Performance Transactional Event Processing
Abstract. This paper presents a transactional framework for low-latency, high-performance, concurrent event processing in Java. At the heart of our framework lies Reflexes, a restricted programming model for highly responsive systems. A Reflex task is an event processor that can run at a higher priority and preempt any other Java thread, including the garbage collector. It runs in an obstruction-free manner with time-oblivious code. We extend Reflexes with a publish/subscribe communication system, itself based on an optimistic transactional event processing scheme, that provides efficient coordination between time-critical, low-latency tasks.We report on the comparison with a commercial JVM, and show that it is possible for tasks to achieve 50 µs response times with way less than 1% of the executions failing to meet their deadlines.
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