Quality-Driven Disorder Handling for M-way Sliding Window Stream Joins

Sliding window join is one of the most important operators for stream applications. To produce high quality join results, a stream processing system must deal with the ubiquitous disorder within input streams which is caused by network delay, asynchronous source clocks, etc. Disorder handling involves an inevitable tradeoff between the latency and the quality of produced join results. To meet different requirements of stream applications, it is desirable to provide a user-configurable result-latency vs. result-quality tradeoff. Existing disorder handling approaches either do not provide such configurability, or support only user-specified latency constraints. In this work, we advocate the idea of quality-driven disorder handling, and propose a buffer-based disorder handling approach for sliding window joins, which minimizes sizes of input-sorting buffers, thus the result latency, while respecting user-specified result-quality requirements. The core of our approach is an analytical model which directly captures the relationship between sizes of input buffers and the produced result quality. Our approach is generic. It supports m-way sliding window joins with arbitrary join conditions. Experiments on real-world and synthetic datasets show that, compared to the state of the art, our approach can reduce the result latency incurred by disorder handling by up to 95% while providing the same level of result quality.Comment: 12 pages, 11 figures, IEEE ICDE 201

Functional features of gene expression profiles differentiating gastrointestinal stromal tumours according to KIT mutations and expression

<p>Abstract</p> <p>Background</p> <p>Gastrointestinal stromal tumours (GISTs) represent a heterogeneous group of tumours of mesenchymal origin characterized by gain-of-function mutations in <it>KIT </it>or <it>PDGFRA </it>of the type III receptor tyrosine kinase family. Although mutations in either receptor are thought to drive an early oncogenic event through similar pathways, two previous studies reported the mutation-specific gene expression profiles. However, their further conclusions were rather discordant. To clarify the molecular characteristics of differentially expressed genes according to GIST receptor mutations, we combined microarray-based analysis with detailed functional annotations.</p> <p>Methods</p> <p>Total RNA was isolated from 29 frozen gastric GISTs and processed for hybridization on GENECHIP^®HG-U133 Plus 2.0 microarrays (Affymetrix). <it>KIT </it>and <it>PDGFRA </it>were analyzed by sequencing, while related mRNA levels were analyzed by quantitative RT-PCR.</p> <p>Results</p> <p>Fifteen and eleven tumours possessed mutations in <it>KIT </it>and <it>PDGFRA</it>, respectively; no mutation was found in three tumours. Gene expression analysis identified no discriminative profiles associated with clinical or pathological parameters, even though expression of hundreds of genes differentiated tumour receptor mutation and expression status. Functional features of genes differentially expressed between the two groups of GISTs suggested alterations in angiogenesis and G-protein-related and calcium signalling.</p> <p>Conclusion</p> <p>Our study has identified novel molecular elements likely to be involved in receptor-dependent GIST development and allowed confirmation of previously published results. These elements may be potential therapeutic targets and novel markers of <it>KIT </it>mutation status.</p

XSiena: The Content-Based Publish/Subscribe System

Just as packet switched networks constituted a major breakthrough in our perception of the information exchange in computer networks so have the decoupling properties of publish/subscribe systems revolutionized the way we look at networking in the context of large scale distributed systems. The decoupling of the components of publish/subscribe systems in time, space and synchronization has created an appealing platform for the asynchronous information exchange among anonymous information producers and consumers. Moreover, the content-based nature of publish/subscribe systems provides a great degree of flexibility and expressiveness as far as construction of data flows is considered. However, a number of challenges and not yet addressed issued still exists in the area of the publish/subscribe systems. One active area of research is directed toward the problem of the efficient content delivery in the content-based publish/subscribe networks. Routing of the information based on the information itself, instead of the explicit source and destination addresses poses challenges as far as efficiency and processing times are concerned. Simultaneously, due to their decoupled nature, publish/subscribe systems introduce new challenges with respect to issues related to dependability and fail-awareness. This thesis seeks to advance the field of research in both directions. First it shows the design and implementation of routing algorithms based on the end-to-end systems design principle. Proposed routing algorithms obsolete the need to perform content-based routing within the publish/subscribe network, pushing this task to the edge of the system. Moreover, this thesis presents a fail-aware approach towards construction of the content-based publish/subscribe system along with its application to the creation of the soft state publish/subscribe system. A soft state publish/subscribe system exposes the self stabilizing behavior as far as transient timing, link and node failures are concerned. The result of this thesis is a family of the XSiena content-based publish/subscribe systems, implementing the proposed concepts and algorithms. The family of the XSiena content-based publish/subscribe systems has been a subject to rigorous evaluation, which confirms the claims made in this thesis

XSiena: The Content-Based Publish/Subscribe System

Just as packet switched networks constituted a major breakthrough in our perception of the information exchange in computer networks so have the decoupling properties of publish/subscribe systems revolutionized the way we look at networking in the context of large scale distributed systems. The decoupling of the components of publish/subscribe systems in time, space and synchronization has created an appealing platform for the asynchronous information exchange among anonymous information producers and consumers. Moreover, the content-based nature of publish/subscribe systems provides a great degree of flexibility and expressiveness as far as construction of data flows is considered. However, a number of challenges and not yet addressed issued still exists in the area of the publish/subscribe systems. One active area of research is directed toward the problem of the efficient content delivery in the content-based publish/subscribe networks. Routing of the information based on the information itself, instead of the explicit source and destination addresses poses challenges as far as efficiency and processing times are concerned. Simultaneously, due to their decoupled nature, publish/subscribe systems introduce new challenges with respect to issues related to dependability and fail-awareness. This thesis seeks to advance the field of research in both directions. First it shows the design and implementation of routing algorithms based on the end-to-end systems design principle. Proposed routing algorithms obsolete the need to perform content-based routing within the publish/subscribe network, pushing this task to the edge of the system. Moreover, this thesis presents a fail-aware approach towards construction of the content-based publish/subscribe system along with its application to the creation of the soft state publish/subscribe system. A soft state publish/subscribe system exposes the self stabilizing behavior as far as transient timing, link and node failures are concerned. The result of this thesis is a family of the XSiena content-based publish/subscribe systems, implementing the proposed concepts and algorithms. The family of the XSiena content-based publish/subscribe systems has been a subject to rigorous evaluation, which confirms the claims made in this thesis

Handling Overload in Publish/Subscribe Systems

Abstract—This paper proposes a new approach for handling overload in Publish/Subscribe systems. We focus on the fact that every service has to cope with the limitations imposed by the external environment (e.g., network congestion) and the limitations resulting directly from within the service itself – e.g., the maximum available computational power. This work seeks to aid Publish/Subscribe mechanisms with the ability to handle both aforementioned constraints in a graceful way, simultaneously ensuring for the most valuable information to be given the highest chance of a successful delivery. I

Highly Available Publish/Subscribe

We propose a novel approach for ensuring the availability of a publish/subscribe (P/S) service with limited resources. Our approach complies with the fully decoupled nature of P/S services

MMPP-based HTTP traffic generation with multiple emulated sources

In this article we propose a new tool, named Raw Packet Sender (RPS), for testing the performance of WWW servers. Our solution allows for testing with arbitrary number of source IP addresses although the tra#c originates from only one physical NIC. In order to better mimic the real life environment we implemented an HTTP session interarrival time generator based on Markov Modulated Poisson Process (MMPP), which can closely match auto-covariance and the marginal distribution of recorded web tra#c traces