Analysing Temporal Relations – Beyond Windows, Frames and Predicates

This article proposes an approach to rely on the standard operators of relational algebra (including grouping and ag- gregation) for processing complex event without requiring window specifications. In this way the approach can pro- cess complex event queries of the kind encountered in appli- cations such as emergency management in metro networks. This article presents Temporal Stream Algebra (TSA) which combines the operators of relational algebra with an analy- sis of temporal relations at compile time. This analysis de- termines which relational algebra queries can be evaluated against data streams, i. e. the analysis is able to distinguish valid from invalid stream queries. Furthermore the analysis derives functions similar to the pass, propagation and keep invariants in Tucker's et al. \Exploiting Punctuation Seman- tics in Continuous Data Streams". These functions enable the incremental evaluation of TSA queries, the propagation of punctuations, and garbage collection. The evaluation of TSA queries combines bulk-wise and out-of-order processing which makes it tolerant to workload bursts as they typically occur in emergency management. The approach has been conceived for efficiently processing complex event queries on top of a relational database system. It has been deployed and tested on MonetDB

Partitioning functions for steteful data parallelism in stream processing

Cataloged from PDF version of article.In this paper we study partitioning functions for stream processing systems that employ stateful data parallelism to improve application throughput. In particular, we develop partitioning functions that are effective under workloads where the domain of the partitioning key is large and its value distribution is skewed. We define various desirable properties for partitioning functions, ranging from balance properties such as memory, processing, and communication balance, structural properties such as compactness and fast lookup, and adaptation properties such as fast computation and minimal migration. We introduce a partitioning function structure that is compact and develop several associated heuristic construction techniques that exhibit good balance and low migration cost under skewed workloads. We provide experimental results that compare our partitioning functions to more traditional approaches such as uniform and consistent hashing, under different workload and application characteristics, and show superior performance

The effect of metacognitive strategy instruction on L2 learner beliefs and listening skills

This pilot study investigated the effect of semester-long strategy-based instruction on learner beliefs and skills in the processing of aural input by adult learners of English as a second language at metacognitive and procedural levels. The study addressed two frequently encountered learner beliefs thought to impede L2 processing of aural input: The little words aren’t important; intonation is merely decorative. Working on the premise that learner beliefs underpin learner strategies for processing aural input and are reflected in learner productive and receptive skills, pre- and post-instruction instruments measured both learners’ awareness of connected speech processes and the functions of intonation, and their ability to segment a continuous speech stream, and to process utterances for speaker intent. Findings using repeated measures analysis of variance support strategy-based metacognitive training in connected speech and stress and intonation to promote listening skills awareness, aid word segmentation, and facilitate understanding utterance content and intended meaning.Published versio

Streaming Aggregation using Reconfigurable Hardware

High throughput and low latency streaming aggregation is essential for many applications that analyze massive volumes of data in real-time. In many cases, high speed stream aggregation can be achieved incrementally by computing partial results for multiple windows. However, for particular problems, temporarily storing all incoming raw data to a single window before processing is more efficient or even the only option. This thesis presents the first FPGA-based single window stream aggregation designs for tuple-based and time-based windowing policies. The proposed approach is able to support challenging queries required in realistic stream processing problems. More precisely, holistic, distributive, and algebraic aggregation functions, as well as custom ones can be supported. Our designs offer aggregation for large number of concurrently active keys and handles large window sizes and frequent aggregations. Maxeler\u27s dataflow engines (DFEs), which suit well the stream processing characteristics, are used to implement the designs. DFEs have a direct feed of incoming data from the network as well as direct access to off-chip DRAM. The tuple-based single window DFE processes up to 8 million tuples-per-second (1.1 Gbps) offering 1-2 orders of magnitude higher throughput than a state-of-the-art stream processing software system. The processing latency is less than 4 usec, 4 orders of magnitude lower latency than software. The time-based single-window stream aggregation DFE offers high processing throughput, up to 150 Mtuples/sec, similar to related GPU systems, which however do not support both time-based and single windows. It also offers an ultra-low processing latency of 1-10 usec, at least 4 orders of magnitude lower than software-based solutions

Test Infrastructure for Address-Event-Representation Communications

Address-Event-Representation (AER) is a communication protocol for transferring spikes between bio-inspired chips. Such systems may consist of a hierarchical structure with several chips that transmit spikes among them in real time, while performing some processing. To develop and test AER based systems it is convenient to have a set of instruments that would allow to: generate AER streams, monitor the output produced by neural chips and modify the spike stream produced by an emitting chip to adapt it to the requirements of the receiving elements. In this paper we present a set of tools that implement these functions developed in the CAVIAR EU project.Unión Europea IST-2001-34124 (CAVIAR)Ministerio de Ciencia y Tecnología TIC-2003-08164-C03-0