TESLA: a formally defined event specification language

The need for timely processing large amounts of information, flowing from the peripheral to the center of a system, is common to different application domains, and it has justified the development of several languages to describe how such information has to be processed. In this paper, we analyze such languages showing how most approaches lack the expressiveness required for the applications we target, or do not provide the precise semantics required to clearly state how the system should behave. Moving from these premises, we present TESLA, a complex event specification language. Each TESLA rule considers incoming data items as notifications of events and defines how certain patterns of events cause the occurrence of others, said to be "complex". TESLA has a simple syntax and a formal semantics, given in terms of a first order, metric temporal logic. It provides high expressiveness and flexibility in a rigorous framework, by offering content and temporal filters, negations, timers, aggregates, and fully customizable policies for event selection and consumption. The paper ends by showing how TESLA rules can be interpreted by a processing system, introducing an efficient event detection algorithm based on automata

Drop the phone and talk to the physical world: Programming the internet of things with Erlang

Abstract-We present ELIOT, an Erlang-based development framework expressly conceived for heterogeneous and massively decentralized sensing/actuation systems: a vision commonly regarded as the "Internet of Things". We choose Erlang due to the functional high-level programming model and the native support for concurrency and distributed programming. Both are assets when developing applications as well as systemlevel functionality in our target domain. Our design enriches the Erlang framework with a custom library for programming sensing/actuation distributed systems along with a dedicated run-time support, while we wipe off unnecessary language and run-time features. We couple the resulting platform with adhoc tools for simulation and testing, supporting developers throughout the development cycle. We assess our solution by implementing three sensor network distributed protocols. A comparison with traditional sensor network programming platforms demonstrates the advantages in terms of terseness of code, readability, and maintainability

REDS: A reconfigurable dispatching system

We present a new publish-subscribe middleware called REDS (REconfigurable Dispatching System) designed to tolerate dynamic reconfigurations of the dispatching infrastructure, like those occurring in scenarios characterized by fluid topologies as in mobile and peer-to-peer networks. We illustrate the modular architecture of REDS, which enables programmers to change the internal configuration of the middleware to suit the deployment scenario, focusing on the aspects concerned with the dynamic reconfiguration of the dispatching network. Keywords. Publish-subscribe, content-based routing, dynamic reconfiguration, mobile and peer-to-peer computing. 1

Inconsistencies in Software Development: Towards a Reference Framework

This paper describes a framework to formalize the concept of inconsistency in software development. This framework will be used to analyze and compare several approaches proposed in literature to deal with the different forms of inconsistencies that may arise in software development

Complex event processing with T-REX

Several application domains involve detecting complex situations and reacting to them. This asks for a Complex Event Processing (CEP) middleware specifically designed to timely process large amounts of event notifications as they flow from the peripheral to the center of the system, to identify the composite events relevant for the application. To answer this need we designed T-Rex, a new CEP middleware that combines expressiveness and efficiency. On the one hand, it adopts a language (TESLA) explicitly conceived to easily and naturally describe composite events. On the other hand, it provides an efficient event detection algorithm based on automata to interpret TESLA rules. Our evaluation shows that the T-Rex engine can process a large number of complex rules with a reduced overhead, even in the presence of challenging workloads

Adapting publish-subscribe routing to traffic demands

Most of currently available content-based publish-subscribe systems that were designed to operate in large scale, wired scenarios, build their routing infrastructure as a set of brokers connected in an acyclic network. The topology of such network is critical for the performance of the system. Depending on the traffic profile, the same topology may provide good performance or be very inefficient. Starting from this consideration, in this paper we first analyze this issue in detail, then we describe a distributed algorithm to address it, by adapting the topology of a content-based publish-subscribe routing network to the application demand