Lazaros Polymenakos

EMPEROR: An OGSA Grid Meta-Scheduler Based on Dynamic Resource Predictions

Scheduling constitutes an integral feature of Grid computing infrastructures, being also a key to realizing several of the Grid promises. In particular, scheduling can maximize the resources available to end users, accelerate the execution of jobs, while also supporting scalable and autonomic management of the resources comprising a Grid. Grid scheduling functionality hinges on middleware components called meta-schedulers, which undertake to automatically distribute jobs across the dispersed heterogeneous resources of a Grid. In this paper we present the design and implementation of a Grid meta-scheduler, which we call EMPEROR. EMPEROR provides a framework for implementing scheduling algorithms based on performance criteria. In implementing a particular instantiation of this framework, we have devised models for predicting host load and memory resources, and accordingly for estimating the running time of a task. These models hinge on time series analysis techniques and take into account results of the cluster computing literature. Apart from incorporating these models, EMPEROR provides fully fledged Grid scheduling functionality, which complies with OGSA standards as the later are reflected in the Globus toolkit. Specifically, EMPEROR interfaces to Globus middleware services (i.e., GSI, MDS, GRAM) towards discovering resources, implementing the scheduling algorithm and ultimately submitting jobs to local scheduling systems. By and large, EMPEROR is one of the few standards based meta-schedulers making use of dynamic scheduling information.

An ontology-based framework for dynamic resource management in ubiquitous computing environments

Ubiquitous computing applications are supported by sophisticated middleware components enabling dynamic discovery, invocation and management of resources, as well as reasoning in cases of uncertainty. This paper advocates semantic Web technologies as primary vehicles to achieve dynamic management of resources in ubiquitous computing infrastructures and services. We introduce a framework for implementing ubiquitous computing services comprising a large number of sensors and perceptive interfaces, emphasizing the role of knowledge bases for dynamic registration and invocation of resources. We present the use of ontology-based mechanisms for controlling sensors and actuators. Moreover, we describe the implementation of a knowledge base server that can leverage different ontology management systems, while also exposing a host to different client access interfaces. The introduced framework has been exploited in implementing real prototype ubiquitous computing services, which we also outline in the paper.

An approach to lightweight deployment of web services

Web Services is gradually becoming the most popular distributed computing paradigm for the Internet. Although several vendor and research efforts are in progress, fully-fledged deployment of Web Services in a wide scale has not been accomplished yet. The present contribution describes a framework for lightweight deployment of Web Services. This framework can be seen as a contribution to a smooth transition step towards a complete large-scale deployment. The paper starts with a description of data access techniques supporting multiple data providers, devised and used in the scope of a European research project. It is illustrated how schemes employed to provide remote transparent access to the data providers evolved to a lightweight Web Services framework.

ɛ-Relaxation and Auction Methods for Separable Convex Cost Network Flow Problems

We consider a generic auction method for the solution of the single commodity, separable convex cost network flow problem. This method provides a unifying framework for the ∈-relaxation method and the auction/sequential shortest path algorithm and, as a consequence, we develop a unified complexity analysis for the two methods. We also present computational results showing that these methods are much faster than earlier relaxation methods, particularly for ill-conditioned problems.

A Formally Specified Ontology Management API as a Registry for Ubiquitous Computing Systems

Recently, several standards have emerged for ontology markup languages that can be used to formalize all kinds of knowledge. However, there are no widely accepted standards yet that define APIs to manage ontological data. Processing ontological information still suffers from the heterogeneity imposed by the plethora of available ontology management systems. Moreover, ubiquitous computing environments usually comprise software components written in a variety of different programming languages, which makes it even more difficult to establish a common ontology management API with programming language agnostic semantics. We implemented an ontological Knowledge Base Server, which can expose the functionality of arbitrary off-the-shelf ontology management systems via a formally specified and well defined API. A case study was carried out in order to demonstrate the feasibility of our approach to use an ontological Knowledge Base Server as a registry for ubiquitous computing systems.

Multimodal web applications: design issues and an implementation framework

Even with recent advances in mark-up languages, content eneration, content transformation tools, and the architecture of multimodal browsers, it is still complex to design, implement and deploy a multimodal web application. A key reason is the absence of an end-to-end solution dealing with all aspects of multimodal web application development. This paper presents the main design issues that are associated with multimodal web applications and proposes a unifying framework for the end-to-end design and implementation of components that support multimodal web applications. It is illustrated that the framework uses existing, standards-based, multi-tier technologies to provide multimodal browsing, content access and transformation, multimodal authoring, and personalisation. Two web applications using this framework are described with results from their evaluation. Furthermore, we position the introduced solution with respect to related state-of-the-art initiatives such as X+V and SALT and show that it addresses several of these design issues.

Aspects of design and implementation of a multi-channel and multi-modal information system

The paper describes an architecture for multi-channel and multi-modal applications. First the design problem is explored and a proposal for a system that can handle multi-modal interaction and delivery of Internet content is proposed. The focus is pertained in some development aspects and the way they are addressed by using state-of-the-art tools. The various components are defined and described in detail. Finally, conclusions and a view of future work on the evolution of such systems is given.

Programmable Grids Framework Enabling QoS in an OGSA Context

Configuring, monitoring and guaranteeing service levels is a key prerequisite towards supporting the wave of emerging Grid computing applications, especially those relating to e-business. Managing QoS across a Grid infrastructure is particularly complex since QoS must be addressed at three different levels: network, middleware and application. Programmable Grids extend programmable networks concepts to Grid infrastructures and can alleviate this complexity. In this paper we elaborate on the importance of network, middleware and application level QoS, and accordingly provide a framework for designing and implementing programmable APIs that can handle QoS. The framework leverages the structure and properties of OGSA services, while exploiting functionality of OGSI containers. Moreover, early implementation experiences with this framework and Globus (GT3) are reported.

Quantized Dialog – A general approach for conversational systems

Abstractr We propose Quantized Dialog, a novel approach for the development of conversational systems. The methodology relies on the semantic quantization and clustering of the dialog utterances in order to reduce the dialog interaction space, making prediction of the next utterance more tractable. The effectiveness of this method is showcased using the goal-oriented dataset of the sixth Dialog System Technology Challenge (DSTC6). We compare the performance of Quantized Dialog based on an n-gram language model for next-utterance prediction against other models that employ popular deep-learning architectures, such as multi-layer neural network classifiers, memory networks, long short-term memory recurrent neural networks and convolutional neural networks. The experimental results demonstrate the promising potential of the new quantized approach in goal-oriented dialog prediction.

Conversational natural language understanding interfacing city event information

The article describes aspects of the development of a conversational natural language understanding (NLU) system done during the first year of the European research project CATCH-2004 (Converse in AThens Cologne and Helsinki) [http://www.catch2004.org]. The project is co-funded by the European Union in the scope of the IST programme (IST 1999-11103).Its objectives focus on multi-modal, multi-lingual conversational natural language access to information systems. The paper emphasises on architecture, and telephony-based speech and NLU components as well as aspects of the implementation of a city event information (CEI) system in English, Finnish, German and Greek. The CEI system accesses two different databases in Athens and Helsinki using a common retrieval interface. Furthermore the paper singles out methodologies involved for acoustic and language model of the speech recognition component, parsing techniques and dialog modelling for the conversational natural language subsystem. For the implementation it outlines an incremental system refinement methodology necessary to adapt the system components to real-life data. It addresses the implementation of language specific characteristics and a common dialog design for all four languages, but also deals with aspects towards a multilingual conversational system. Finally, it presents prospects for further developments of the project.