Hugo Pacheco

Duality plays a fundamental role in many areas of mathematics, computer science, systems
theory and even physics. For example, the familiar concept of Fourier transform is essentially a duality result: an instance of Pontryagin duality, see, for example the standard textbook [Rudin 1962]. Another basic instance, known to undergraduates, is the duality of a finite-dimensional vector spaces V over some field k, and the space of linear maps from V to k, which is itself a finite-dimensional vector space. Building on this self-duality, a fundamental principle in systems theory due to [Kalman 1959] captures the duality between the concepts of observability and controllability (to be explained below). The latter was further extended to automata theory (where controllability amounts to reachability) in [Arbib and Zeiger 1969], and in various papers [Arbib and Manes 1974; 1975a; 1975c; 1975b; 1980a; 1980b] where Arbib and Manes explored algebraic automata theory in a categorical framework; see also the excellent collection of papers [Kalman et al. 1969] where both automata theory and systems theory is presented.

Approaches to dependability and performance are challenged when systems are made up of networks of heterogeneous applications/devices, especially when operating in unpredictable open-world settings. The research community is tackling this problem and exploring means for enabling interoperability at the application level. The EU project CONNECT has developed a generic interoperability mechanism which relies on the on-the-fly synthesis of CONNECTors, that is software bridges that enable and adapt communication among heterogeneous devices. Dependability and Performance are relevant aspects of the system. In our previous work, we have identified generic dependability mechanisms for enhancing the dependability of CONNECTors. In this work, we introduce a set of generic strategies for automating the selection and application of an appropriate dependability mechanism. A case study based on a global monitoring system for environment and security (GMES) is used as a means for demonstrating the approach.

A utilização de novas tecnologias para projetos de automação é hoje uma tendência nos grandes centros urbanos. Porém, no campo, a agricultura carece do uso dessas tecnologias, inclusive, em sistemas e métodos de irrigação e de monitoramento de lavouras, dos quais são em sua grande maioria ultrapassados e inadequados. Consequentemente, isso afeta diretamente todo o setor econômico de uma sociedade. Com isso, faz-se necessário o desenvolvimento de um mecanismo automatizado de controle de irrigação, possibilitando uma maior eficiência e eficácia no processo de irrigação. Para tanto, o objetivo deste trabalho foi o desenvolvimento de um sistema de hardware e software capaz de tornar o processo de irrigação mais simples para o agricultor. Esse sistema consiste no controle e monitoramento da irrigação por meio de uma aplicação desenvolvida para computadores pessoais e através da internet, tendo em vista a mobilidade proporcionada para acesso do sistema em qualquer lugar do mundo. Além das vantagens práticas e econômicas, o sistema automatizado de irrigação possui um simples desenvolvimento, e utiliza materiais de baixo custo, o que torna viável sua implantação em grandes, médias e, inclusive, em pequenas lavouras.

Deduplication has proven to be a valuable technique for eliminating duplicate data in backup and archival systems and is now being applied to new storage environments with distinct requirements and performance trade-offs. Namely, deduplication system are now targeting large-scale cloud computing storage infrastructures holding unprecedented data volumes with a significant share of duplicate content.

It is however hard to assess the usefulness of deduplication in particular settings and what techniques provide the best results. In fact, existing disk I/O benchmarks follow simplistic approaches for generating data content leading to unrealistic amounts of duplicates that do not evaluate deduplication systems accurately. Moreover, deduplication systems are now targeting heterogeneous storage environments, with specific duplication ratios, that benchmarks must also simulate.

We address these issues with DEDISbench, a novel micro-benchmark for evaluating disk I/O performance of block based deduplication systems. As the main contribution, DEDISbench generates content by following realistic duplicate content distributions extracted from real datasets. Then, as a second contribution, we analyze and extract the duplicates found on three real storage systems, proving that DEDISbench can easily simulate several workloads.

The usefulness of DEDISbench is shown by comparing it with Bonnie++ and IOzone open-source disk I/O micro-benchmarks on assessing two open-source deduplication systems, Opendedup and Lessfs, using Ext4 as a baseline. Our results lead to novel insight on the performance of these file systems.

Topic-based publish/subscribe is at the core of many distributed systems, ranging from application integration middleware to news dissemination. Therefore, much research was dedicated to publish/subscribe architectures and protocols, and in particular to the design of overlay networks for decentralized topic-based routing and efficient message dissemination. Nonetheless, existing systems fail to take full advantage of shared interests when disseminating information, hence suffering from high maintenance and traffic costs, or construct overlays that cope poorly with the scale and dynamism of large networks. In this paper we present StaN, a decentralized protocol that optimizes the properties of gossip-based overlay networks for topic- based publish/subscribe by sharing a large number of physical connections without disrupting its logical properties. StaN relies only on local knowledge and operates by leveraging common interests among participants to improve global resource usage and promote topic and event scalability. The experimental evaluation under two real workloads, both via a real deployment and through simulation shows that StaN provides an attractive infrastructure for scalable topic-based publish/subscribe.

Interested in formalizing the generation of fast running code for linear algebra applications, the authors show how an index-free, calculational approach to matrix algebra can be developed by regarding matrices as morphisms of a category with biproducts. This shifts the traditional view of matrices as indexed structures to a type-level perspective analogous to that of the pointfree algebra of programming. The derivation of fusion, cancellation and abide laws from the biproduct equations makes it easy to calculate algorithms implementing matrix multiplication, the central operation of matrix algebra, ranging from its divide-and-conquer version to its vectorization implementation.
From errant attempts to learn how particular products and coproducts emerge from biproducts, not only blocked matrix algebra is rediscovered but also a way of extending other operations (e.g. Gaussian elimination) blockwise, in a calculational style, is found.
The prospect of building biproduct-based type checkers for computer algebra systems such as MatlabTM is also considered.

Background

Due to their different propagation times, visual and auditory signals from external events arrive at the human sensory receptors with a disparate delay. This delay consistently varies with distance, but, despite such variability, most events are perceived as synchronic. There is, however, contradictory data and claims regarding the existence of compensatory mechanisms for distance in simultaneity judgments.

Principal Findings

In this paper we have used familiar audiovisual events – a visual walker and footstep sounds – and manipulated the number of depth cues. In a simultaneity judgment task we presented a large range of stimulus onset asynchronies corresponding to distances of up to 35 meters. We found an effect of distance over the simultaneity estimates, with greater distances requiring larger stimulus onset asynchronies, and vision always leading. This effect was stronger when both visual and auditory cues were present but was interestingly not found when depth cues were impoverished.

Significance

These findings reveal that there should be an internal mechanism to compensate for audiovisual delays, which critically depends on the depth information available.