Ralph Deters

Dynamic Courseware Generation on the WWW

We have developed a tool for the authoring of adaptive CAL courses, called “Dynamic Courseware Generator” (DCG). It generates an individual course according to the learners goals and previous knowledge and dynamically adapts the course according to the learners success in acquiring knowledge. The DCG runs on a WWW server. The learner receives from this server an individualized course targeted to a specified goal. Afterwards, s/he is adaptively guided by the course through a space of teaching materials on the WWW. Unlike other CAL courses on the WWW, a course produced by the DCG is interactive, it tests the learner’s knowledge and dynamically adapts to the students progress. The authoring tool can be used also for collaborative authoring and learning.

Improving fault-tolerance by replicating agents

Despite the considerable efforts spent on developing multi-agent systems the actual number of deployed systems is surprisingly small. One of the reasons for the significant gap between developed and deployed systems is their brittleness.The absence of centralized control components makes it difficult to detect and treat failures of individual agents thus risking fault-propagation that can seriously impact the performance of the system. Using redundancy by replication of individual agents within a multi-agent system is one possible approach for improving fault-tolerance. Unfortunately the introduction of replicates leads to increased complexity and system load. In this paper we examine the use of transparent agent replication, a technique in which the replicates of agents appear and act as one entity thus avoiding an increase in system complexity and minimizing additional system loads. The paper defines transparent agent replication and identifies the key challenges in using it. Special attention is given to the inter-agent communication, read/write consistency, resource locking, resource synthesis and state synchronization. An implementation of the transparent agent replication for the FIPA-OS framework is presented and the results of testing it within a real-world multi-agent system are shown.

The costs of using JXTA

Project JXTA is an open-source effort to specify the standard protocols for peer-to-peer communication and collaboration. We propose a JXTA performance model and present results obtained by benchmarking the JXTA 1.0 reference implementation in Java. We focus on the performance evaluation of typical peer operations and consequences for the peer network, the user and the developer. The important trade-off between peer startup latency and the maintenance of the local cache is shown and discussed. The throughput limits of pipes, the core JXTA communication concept, are also measured in a LAN environment for smooth and bursty traffic. The results indicate that the limiting factor for reliable throughput is the number of messages rather than size in bytes, as well as that small JXTA messages carry an excessive overhead of control data. Important performance issues and trade-offs are identified and explored, as a basis for the formulation of guidelines for system designers and simulation-based research of JXTA networks.

SOA's Last Mile-Connecting Smartphones to the Service Cloud

Modern Smartphones are the fastest growing computing platforms capable of consuming web services. However, due to their form factor these mobile computing devices face many challenges and constrains when engaging service providers. How to overcome these challenges and how to link smartphones to the service cloud is one of the key issues that will have a major impact on the further growth of the software-as-a-service (SaaS) and software-plus-service (S+S) deployments.This paper focuses on the use of a cloud hosted middleware layer that acts as a personal service bus (PSB). Similar to an ESB the PSB offers a user and device customized view on services of the cloud by enabling protocol transformation, request/response augmentation, message optimization, caching and pre-fetching. The paper also reports on an evaluation of the PSB called Mobile Cloud Computing Middleware (MCCM) with the G1 (HTC).

3LS - a peer-to-peer network simulator

Peer-to-peer (p2p) networks are the latest addition to the already large distributed systems family. With a strong emphasis on self-organization, decentralization and autonomy of the participating nodes, p2p-networks tend to be more scalable, robust and adaptive than other forms of distributed systems. The much-publicized success of p2p-networks for file-sharing and cycle-sharing have resulted in an increased awareness and interest into the p2p protocols and applications. However, p2p-networks are difficult to study due to their size and the complex interdependencies between users, application, protocol and network. We present a 3-level simulator designed to study complex p2p networks.

An efficient dual caching strategy for web service-enabled PDAs

PDAs have evolved over the years from resource constrained devices that supported only the most basic tasks to powerful handheld computing devices. However, the most significant step in the evolution of PDAs was the introduction of wireless connectivity which enabled them to host applications that require internet connectivity like email, web browsers and maybe most importantly smart/rich clients. Being able to host smart clients allows the users of PDAs to seamlessly access the IT resources (e.g. legacy apps) of their organizations. One increasingly popular way of enabling access to IT resources is by using Web Services (WS) [14]. This trend has been aided by the rapid availability of Web Service (WS) packages/tools, most notably the efforts of the Apache group [1] and IDE vendors (e.g., Microsofts Visual Studio [2], IBMs Eclipse [3]). Using IDE tools and other software packages it is fairly easy for programmers to expose application interfaces and/or consume existing interfaces leading to a gradual replacement of the current web server centric approaches (e.g. ASP, JSP, Servlets, CGI scripts) with WS centric approach. This paper focuses on the challenges of enabling PDAs to host Web Services consumers and introduces a dual caching approach to overcome problems arising from temporarily loss of connectivity and fluctuations in bandwidth.

Building a P2P forum system with JXTA

Decentralized file-sharing systems like Napster and Gnutella have popularized the peer-to-peer approach, which emphasizes the use of distributed resources in a decentralized manner. Peer-to-peer (P2P) systems are a relatively new addition to the large area of distributed systems. Their emphasis on sharing distributed resources, self-organization and use of discovery mechanisms sets them apart from other forms of distributed computing. Avoiding centralized components, and extensive resource/service sharing allows P2P systems to outperform other forms of distributed systems with regards to scalability and robustness due to load distribution and the avoidance of bottlenecks and single points of failure. This paper has two aims; firstly to report on the use of JXTA in converting a server-centric legacy forum system into a P2P system. It also attempts to encourage others in redesigning existing client-server systems into P2P applications as a way of to better understand and evaluate the costs and benefits of this technology.

Architectural design for resilience

Resilience has become a new nonfunctional requirement for information systems. Many design decisions have to be made at the architectural level in order to deliver an information system with the resilience property. This paper discusses the relationships between resilience and other architectural properties such as scalability, reliability, and consistency. A corollary is derived from the CAP theorem, and states that it is impossible for a system to have all three properties of consistency, resilience and partition-tolerance. We present seven architectural constraints for resilience. The constraints are elicited from good architectural practices for developing reliable and fault-tolerant systems and the state-of-the-art technologies in distributed computing. These constraints provide a comprehensive reference for architectural design towards resilience.

The JXTA performance model and evaluation

Project JXTA is an open-source effort to formulate and implement the core peer-to-peer (p2p) networking and collaboration protocols. A JXTA peer network is a complex overlay, constructed on top of the physical network, with its own identification scheme and routing. This paper reviews the performance of the JXTA networks using benchmarking, based on the proposed performance model.The two major versions of thc JXTA protocol implementations (Versions 1.0 and 2.0) are surveyed and discussed.

Towards Knowledge Discovery in Big Data

Analytics-as-a-Service (AaaS) has become indispensable because it affords stakeholders to discover knowledge in Big Data. Previously, data stored in data warehouses follow some schema and standardization which leads to efficient data mining. However, the Big Data epoch has witnessed the rise of structured, semi-structured, and unstructured data, a trend that motivated enterprises to employ the NoSQL data storages to accommodate the high-dimensional data. Unfortunately, the existing data mining techniques which are designed for schema-oriented storages are non-applicable to the unstructured data style. Thus, the AaaS though still in its infancy, is gaining widespread attention for its ability to provide novel ways and opportunities to mine the heterogeneous data. In this paper, we discuss our AaaS tool that performs terms and topics extraction and organization from unstructured data sources such as NoSQL databases, textual contents (e.g., websites), and structured sources (e.g. SQL). The tool is built on methodologies such as tagging, filtering, association maps, and adaptable dictionary. The evaluation of the tool shows high accuracy in the mining process.