Full mobile agent interoperability in an IEEE-FIPA context

The existence of heterogeneous mobile agent systems hinders the interoperability of mobile agents. Several solutions exist, but they are limited in some aspects. This article proposes a full interoperability solution, in the context of the IEEE-FIPA agent standards, composed of three parts. The first part is a simple language-independent agent interface that enables agents to visit locations with different types of middlewares. The second part is a set of design models for the middlewares to support agents developed for different programming languages and architectures. And the third part is a method based on agents with multiple codes and a common agent data encoding mechanism to enable interoperability between middlewares that do not support the same programming languages. Furthermore two agent interoperability implementations, and its corresponding performance comparison, carried out over the JADE and AgentScape agent middlewares are presented.     

MHS: A distributed metadata management strategy

This paper proposes a novel distributed metadata management strategy to efficiently handle different metadata workloads. It can deliver high performance and scalable metadata service through four techniques, including directory conversion metadata, mimic hierarchical directory structure, flexible partition methods targeted different kinds of metadata of diverse characteristics, and the application of database to metadata backend. Using micro-benchmarks and a prototype system, we firstly demonstrate the performance superiority of our strategy compared to Lazy Hybrid, and then present the detailed performance results and analysis of our strategy on different MDS scales.     

An energy-efficient mobile transaction processing method using random back-off in wireless broadcast environments

Broadcast is widely accepted as an efficient technique for disseminating data to a large number of mobile clients over a single or multiple channels. Due to the limited uplink bandwidth from mobile clients to server, conventional concurrency control methods cannot be directly applied. There has been many researches on concurrency control methods for wireless broadcast environments. However, they are mostly for read-only transactions or do not consider exploiting cache. They also suffer from the repetitive aborts and restarts of mobile transactions when the access patterns of mobile transactions are skewed. In this paper, we propose a new optimistic concurrency control method suitable for mobile broadcast environments. To prevent the repetitive aborts and restarts of mobile transactions, we propose a random back-off technique. To exploit the cache on mobile clients, our method keeps the read data set of mobile transactions and prefetches those data items when the mobile transactions are restarted. As other existing optimistic concurrency control methods for mobile broadcast environments does, it works for both read-only and update transactions. Read-only transactions are validated and locally committed without using any uplink bandwidth. Update transactions are validated with forward and backward validation, and committed after final validation consuming a small amount of uplink bandwidth. Our performance analysis shows that it significantly decreases uplink and downlink bandwidth usage compared to other existing methods.     

An improved lossless data hiding scheme based on image VQ-index residual value coding

Copyright protection and information security have become serious problems due to the ever growing amount of digital data over the Internet. Reversible data hiding is a special type of data hiding technique that guarantees not only the secret data but also the cover media can be reconstructed without any distortion. Traditional schemes are based on spatial, discrete cosine transformation (DCT) and discrete wavelet transformation (DWT) domains. Recently, some vector quantization (VQ) based reversible data hiding schemes have been proposed. This paper proposes an improved reversible data hiding scheme based on VQ-index residual value coding. Experimental results show that our scheme outperforms two recently proposed schemes, namely side-match vector quantization (SMVQ)-based data hiding and modified fast correlation vector quantization (MFCVQ)-based data hiding.     

Using phrases as features in email classification

In this paper, we report our experience on the use of phrases as basic features in the email classification problem. We performed extensive empirical evaluation using our large email collections and tested with three text classification algorithms, namely, a naive Bayes classifier and two k-NN classifiers using TF-IDF weighting and resemblance respectively. The investigation includes studies on the effect of phrase size, the size of local and global sampling, the neighbourhood size, and various methods to improve the classification accuracy. We determined suitable settings for various parameters of the classifiers and performed a comparison among the classifiers with their best settings. Our result shows that no classifier dominates the others in terms of classification accuracy. Also, we made a number of observations on the special characteristics of emails. In particular, we observed that public emails are easier to classify than private ones.     

WSDL and UDDI extensions for version support in web services

Versioning is an important aspect of web service development, which has not been adequately addressed so far. In this article, we propose extensions to WSDL and UDDI to support versioning of web service interfaces at development-time and run-time. We address service-level and operation-level versioning, service endpoint mapping, and version sequencing. We also propose annotation extensions for developing versioned web services in Java. We have tested the proposed solution for versioning in two real-world environments and identified considerable improvements in service development and maintenance efficiency, improved service reuse, and simplified governance.     

Managing requirements specifications for product lines - An approach and industry case study

Software product line development has emerged as a leading approach for software reuse. This paper describes an approach to manage natural-language requirements specifications in a software product line context. Variability in such product line specifications is modeled and managed using a feature model. The proposed approach has been introduced in the Swedish defense industry. We present a multiple-case study covering two different product lines with in total eight product instances. These were compared to experiences from previous projects in the organization employing clone-and-own reuse. We conclude that the proposed product line approach performs better than clone-and-own reuse of requirements specifications in this particular industrial context.     

An overhead and resource contention aware analytical model for overloaded Web servers

A Web server, when overloaded, shows a severe degradation of goodput initially, with the eventual settling of goodput as load increases further. Traditional performance models have failed to capture this behavior. In this paper, we propose an analytical model, which is a two-stage and layered queuing model of the Web server, which is able to reproduce this behavior. We do this by explicitly modelling the overhead processing, the user abandonment and retry behavior, and the contention for resources, for the FIFO and LIFO queuing disciplines. We show that LIFO provides better goodput in most overload situations. We compare our model predictions with experimental results from a test bed and find that our results match well with measurements.     

Performance analysis of security aspects by weaving scenarios extracted from UML models

Aspect-oriented modeling (AOM) allows software designers to describe features that address pervasive concerns separately as aspects, and to systematically incorporate the features into a design model using model composition techniques. The goal of this paper is to analyze the performance effects of different security features that may be represented as aspect models. This is part of a larger research effort to integrate methodologies and tools for the analysis of security and performance properties early in the software development process. In this paper, we describe an extension to the AOM approach that provides support for performance analysis. We use the performance analysis techniques developed previously in the PUMA project, which take as input UML models annotated with the standard UML Profile for Schedulability, Performance and Time (SPT), and transform them first into Core Scenario Model (CSM), and then into different performance models. The composition of the aspects with the primary (base) model is performed at the CSM level. A new formal definition of CSM properties and operations is described as a foundation for scenario-based weaving. The proposed approach is illustrated with an example that utilizes two standards, TPC-W and SSL.