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Publicações

Publicações por CRACS

2015

Liquid Intersection Types

Autores
Pereira, M; Alves, S; Florido, M;

Publicação
ELECTRONIC PROCEEDINGS IN THEORETICAL COMPUTER SCIENCE

Abstract
We present a new type system combining refinement types and the expressiveness of intersection type discipline. The use of such features makes it possible to derive more precise types than in the original refinement system. We have been able to prove several interesting properties for our system (including subject reduction) and developed an inference algorithm, which we proved to be sound.

2015

A Typed Language for Events

Autores
Alves, S; Broda, S; Fernandez, M;

Publicação
LOGIC-BASED PROGRAM SYNTHESIS AND TRANSFORMATION (LOPSTR 2015)

Abstract
We define a general typed language to deal with the notion of event in the context of access control systems. We distinguish between generic events, which represent the kind of actions that can occur in a system, and specific events, which represent actual occurrences of those kinds of actions. A relation is given associating specific to generic events, as well as a method for obtaining intervals from a history of events. We describe applications in access control systems with obligations.

2015

Towards programmable coordination of unmanned vehicle networks

Autores
Marques E.R.B.; Ribeiro M.; Pinto J.; Sousa J.B.; Martins F.;

Publicação
IFAC-PapersOnLine

Abstract
The use of unmanned vehicle networks for diverse applications is becoming widespread. It is generally hard to program unmanned vehicle networks as a "whole", however. The coordination of multiple vehicles requires careful planning through intricate human intervention, and a high degree of informality is implied in what concerns the specification of a "network program" for an application scenario. In this context, we have been developing a programming language for expressing global specifications of coordinated behavior in unmanned vehicle networks, the Networked Vehicles' Language (NVL). In this paper we illustrate the use of the language for a thermal pollution plume tracking scenario employing unmanned underwater vehicles.

2015

NVL: a coordination language for unmanned vehicle networks

Autores
Marques, ERB; Ribeiro, M; Pinto, J; Sousa, JB; Martins, F;

Publicação
30TH ANNUAL ACM SYMPOSIUM ON APPLIED COMPUTING, VOLS I AND II

Abstract
The coordinated use of multiple unmanned vehicles over a network can be employed for numerous real-world applications. However, multi-vehicle operations are often deployed through a patchwork of separate components that informally "glue" together during operation, as they are hard to program as a "whole". With this aim, we developed the Networked Vehicles' Language (NVL) for coordinated control of unmanned vehicle networks. A single NVL program expresses an on-the-fly selection of multiple vehicles and their allocation to cooperative tasks, subject to time, precedence, and concurrency constraints. We present the language through an example application involving unmanned underwater vehicles (UUVs) and unmanned aerial vehicles (UAVs), the core design and implementation traits, and results from simulation and field test experiments.

2015

Protocol-Based Verification of Message-Passing Parallel Programs

Autores
Lopez, HA; Marques, ERB; Martins, F; Ng, N; Santos, C; Vasconcelos, VT; Yoshida, N;

Publicação
ACM SIGPLAN NOTICES

Abstract
We present ParTypes, a type-based methodology for the verification of Message Passing Interface (MPI) programs written in the C programming language. The aim is to statically verify programs against protocol specifications, enforcing properties such as fidelity and absence of deadlocks. We develop a protocol language based on a dependent type system for message-passing parallel programs, which includes various communication operators, such as point-to-point messages, broadcast, reduce, array scatter and gather. For the verification of a program against a given protocol, the protocol is first translated into a representation read by VCC, a software verifier for C. We successfully verified several MPI programs in a running time that is independent of the number of processes or other input parameters. This contrasts with alternative techniques, notably model checking and runtime verification, that suffer from the state-explosion problem or that otherwise depend on parameters to the program itself. We experimentally evaluated our approach against state-of-the-art tools for MPI to conclude that our approach offers a scalable solution.

2015

Delay Accounting Optimization Procedure to Enhance End-to-End Delay Estimation in WSNs

Autores
Pinto, P; Pinto, A; Ricardo, M;

Publicação
WIRELESS INTERNET (WICON 2014)

Abstract
Real-time monitoring applications may generate delay sensitive traffic that is expected to be delivered within a firm delay boundary in order to be useful. In this context, a previous work proposed an End-to-End Delay (EED) estimation mechanism for Wireless Sensor Networks (WSNs) to preview potential useless packets, and to early discard them in order to save processing and energy resources. Such estimation mechanism accounts delays using timers that make use of an Exponentially Weighted Moving Average (EWMA) function where the smoothing factor is a constant defined prior to the WSN deployment. Later experiments showed that, in order to enhance the estimation results, such smoothing factor should be defined as a function of the network load. The current work proposes an optimization of the previous estimation mechanism that works by evaluating the network load and by adapting the smoothing factor of the EWMA function accordingly. Results show that this optimization leads to a more accurate EED estimation for different network loads.

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