Finer Garbage Collection in Lindacap

As open systems persist, garbage collection (GC) can be a vital aspect in managing system resources. Although garbage collection has been proposed for the standard Linda, it was a rather course-grained mechanism. This finer-grained method is offered in Lindacap, a capability-based coordination system for open distributed systems. Multicapabilities in Lindacap enable tuples to be uniquely referenced, thus providing sufficient information on the usability of tuples (data) within the tuple-space. This paper describes the garbage collection mechanism deployed in Lindacap, which involves selectively garbage collecting tuples within tuple-spaces. The authors present the approach using reference counting, followed by the tracing (mark-and-sweep) algorithm to garbage collect cyclic structures. A time-to-idle (TTI) technique is also proposed, which allows for garbage collection of multicapability regions that are being referred to by agents but are not used in a specified length of time. The performance results indicate that the incorporation of garbage collection techniques adds little overhead to the overall performance of the system. The difference between the average overhead caused by the mark-and-sweep and reference counting is small, and can be considered insignificant if the benefits brought by the mark-and-sweep is taken into account.

Predicting Temporal Exceptions in Concurrent Workflows

Current Workflow Management Systems (WfMS) are capable of managing simultaneous workflows designed to support different business processes of an organization. These departmental workflows are considered to be interrelated since they are often executed concurrently and are required to share a limited number of resources. However, unexpected events from the business environment and lack of proper resources can cause delays in activities. Deadline violations caused by such delays are called temporal exceptions. Predicting temporal exceptions in concurrent workflows is a complex problem since any delay in a task can cause a ripple effect on the remaining tasks from the parent workflow as well as from the other interrelated workflows. In addition, different types of loops are often embedded in the workflows for representing iterative activities, and presence of such control flow patterns in workflows can further increase the difficulty in estimation of task completion time. In this chapter, the authors describe a critical path based approach for predicting temporal exceptions in concurrent workflows that are required to share limited resources. This approach allows predicting temporal exceptions in multiple attempts while workflows are being executed. The accuracy of the proposed prediction algorithm is analyzed based on a number of simulation scenarios. The result shows that the proposed algorithm is effective in predicting exceptions for instances where long duration tasks are scheduled (or executed) at the early phase of the workflow.

A Model for Ranking and Selecting Integrity Tests in a Distributed Database

Checking the consistency of a database state generally involves the execution of integrity tests on the database, which verify whether the database is satisfying its constraints or not. This paper presents the various types of integrity tests as reported in previous works and discusses how these tests can significantly improve the performance of the constraint checking mechanisms without limiting to a certain type of test. Having these test alternatives and selecting the most suitable test is an issue that needs to be tackled. In this regard, the authors propose a model to rank and select the suitable test to be evaluated given several alternative tests. The model uses the amount of data transferred across the network, the number of sites involved, and the amount of data accessed as the parameters in deciding the suitable test. Several analyses have been performed to evaluate the proposed model, and results show that the model achieves a higher percentage of local processing as compared to the previous selected strategies.

The Role of Physical Affordances in Multifunctional Mobile Device Design

As designers of mobile/media-rich devices continue to incorporate more features/functionality, the evolution of interfaces will become more complex. Meanwhile, users cognitive models must be aligned with new device capabilities and corresponding physical affordances. In this paper, the authors argue that based on HCI design theory, users approach objects by building mental models starting with physical appearance. Findings suggest that users who embrace a device’s multifunctionality are prevented from taking full advantage of an array of features due to an apparent cognitive constraint caused by a lack of physical controls. The authors submit that this problem stems from established mental models and past associated behaviors of both mobile and non-mobile interactive devices. In conclusion, users expressed a preference for immediate access and use of certain physical device controls within a multi-tasking environment, suggesting that as mobile computing becomes more prevalent, physical affordances in multifunctional devices may remain or increase in importance.

Quality of Service for Multimedia and Real-Time Services

New web technologies have encouraged the deployment of various network applications that are rich with multimedia and real-time services. These services demand stringent requirements are defined through Quality of Service (QoS) parameters such as delay, jitter, loss, etc. To guarantee the delivery of these services QoS routing algorithms that deal with multiple metrics are needed. Unfortunately, QoS routing with multiple metrics is considered an NP-complete problem that cannot be solved by a simple algorithm. This paper proposes three source based QoS routing algorithms that find the optimal path from the service provider to the user that best satisfies the QoS requirements for a particular service. The three algorithms use the same filtering technique to prune all the paths that do not meet the requirements which solves the complexity of NP-complete problem. Next, each of the three algorithms integrates a different Multiple Criteria Decision Making method to select one of the paths that have resulted from the route filtering technique. The three decision making methods used are the Analytic Hierarchy Process (AHP), Multi-Attribute Utility Theory (MAUT), and Kepner-Tregoe KT. Results show that the algorithms find a path using multiple constraints with a high ability to handle multimedia and real-time applications.

Virtual Telemedicine and Virtual Telehealth

Telemedicine is modern technology that is employed to provide low cost, high standard medical facilities to the people of remote areas. Store-and-Forward method of telemedicine suits more to the progressive countries like Pakistan as not only is it easy to set up but it also has a very cheap operating cost. However, the high response time taken by store & forward telemedicine becomes a critical factor in emergency cases, where each minute has a price. The response time factor can be overcome by using virtual telemedicine approach. In virtual telemedicine, a Clinical Decision Support System (CDSS) is deployed at rural station. The CDSS is intelligent enough to diagnose a patient’s disease and prescribe proper medication. In case the CDSS cannot answer a query, the CDSS immediately sends an e-mail to a medical expert (doctor), and when the response is received, the CDSS knowledge-base is updated for future queries. In this chapter, the authors not only report a NL-based CDSS that can answer NL queries, but also present a complete architecture of a virtual telemedicine setup.

P2P-NetPay

Micro-payment systems are becoming an important part of peer-to-peer (P2P) networks. The main reason for this is to address the “free-rider” problem in most existing content sharing systems. The authors of this chapter have developed a new micro-payment system for content sharing in P2P networks called P2P-Netpay. This is an offline, debit based protocol that provides a secure, flexible, usable, and reliable credit service in peer-to-peer networks ensuring equitable participation by all parties. The authors have carried out an assessment of micro-payment against non-micro-payment credit systems for file sharing applications. The chapter reports on the design of our experiment and results of an end user evaluation. The chapter then discusses the performance of the credit model, comparing it to a non-micro-payment credit model. Through evaluation of the proposed system and comparison with other existing systems, the authors find that the new approach eliminates the “free-rider” problem. The chapter analyses a heuristic evaluation performed by a set of evaluators and presents directions for research aiming to improve the overall satisfaction and efficiency of this model for peers.

Ripple Effect in Web Applications

The number of internet web applications is rapidly increasing in a variety of fields and not much work has been done for ensuring their quality, especially after modification. Modifying any part of a web application may affect other parts. If the stability of a web application is poor, then the impact of modification will be costly in terms of maintenance and testing. Ripple effect is a measure of the structural stability of source code upon changing a part of the code, which provides an assessment of how much a local modification in the web application may affect other parts. Limited work has been published on computing the ripple effect for web application. In this paper, the authors propose, a technique for computing ripple effect in web applications. This technique is based on direct-change impact analysis and dependence analysis for web applications developed in the .Net environment. Also, a complexity metric is proposed to be included in computing the ripple effect in web applications.

Quality of Service Management by Third Party in the Evolved Packet System

The chapter investigates the capabilities for open access to quality of service management in the Evolved Packet System. Based on the analysis of requirements for policy and charging control in the Evolved Packet Core, functions for quality of service (QoS) management and charging, available for third party applications, are identified. The functionality of Open Service Access (OSA) and Parlay X interfaces is evaluated for support of dynamic QoS control on user sessions. An approach to development of OSA-compliant application programming interfaces for QoS management in the Evolved Packet System is presented. The interface’s methods are mapped onto the messages of network control protocols. Aspects of interface implementation are discussed, including interface to protocol conversion.

A Pattern Language for Knowledge Discovery in a Semantic Web Context

Ontologies are used to represent data and share knowledge of a specific domain, and in recent years they tend to be used in many applications such as database integration, peer-to-peer systems, e-commerce, semantic web services, bioinformatics, or social networks. Feeding ontological domain knowledge into those applications has proven to increase flexibility and inter-operability and interpretability of data and knowledge. As more data is gathered/generated by those applications, it becomes important to analyze and transform it to meaningful information. One possibility is to use data mining techniques to extract patterns from those large amounts of data. One challenging general problem in mining ontological data is taking into account not only domain concepts, properties and instances, but also hierarchical structures of those concepts and properties. In this paper, the authors research the specific problem of extracting ontology-based sequential patterns.