Scientific Journals and Yearbooks Published at SAS

Article List

Computing and Informatics

Volume 23, 2004, No. 4


  Publishing H2O pluglets in UDDI registries

OGSA, UDDI, H2O, distributed computing, grids

Interoperability and standards, such as Grid Services are a focus of current Grid research. The intent is to facilitate resource virtualization, and to accommodate the intrinsic heterogeneity of resources in distributed environments. It is important that new and emerging metacomputing frameworks conform to these standards, in order to ensure interoperability with other grid solutions. In particular, the H2O metacomputing system offers several benefits, including lightweight operation, user-configurability, and selectable security levels. Its applicability would be enhanced even further through support for grid services and OGSA compliance. Code deployed into the H2O execution containers is referred to as pluglets. These pluglets constitute the end points of services in H2O, services that are to be made known through publication in a registry. In this contribution, we discuss a system pluglet, referred to as OGSAPluglet, that scans H2O execution containers for available services and publishes them into one or more UDDI registries. We also discuss in detail the algorithms that manage the publication of the appropriate WSDL and GSDL documents for the registration process.

Computing and Informatics. Volume 23, 2004, No. 4: 305-315.

  A Comparative Study of Queue, Delay, and Loss Characteristics of AQM Schemes in QoS-enabled Networks

Network characteristic, simulation technique, queue schemes, per-node queueing, per-flow en-to-end behavior, Internet QoS

One of the major component in a QoS-enabled network is active queue management (AQM). Over the last decade numerous AQM schemes have been proposed in the literature. However, much recent work has focused on improving AQM performance through alternate approaches. This study focuses on an unbiased comparative evaluation of the various proposals. The evaluation methodology adopted is the following: we first define the relationship between the terminologies used in this paper, briefly introduce the queue, delay, and loss characteristics-- a subset of network characteristics that can be used to describe the behavior of network entities, and give their mathematical description. Next, we present a method that would be a successful case study based on the NS simulation technique and simulation-based comparisons of AQM schemes chosen, which will help understand how they differ from in terms of per-node queueing information and per-flow end-to-end behavior. Simulation results showed that PI schemes, a feedback-based mechanism, can assist delay sensitive applications to adapt dynamically to underlying network and to stabilize the end-to-end QoS within an acceptable requirement. To understand this attribute and behavior is important for the proper design of queue disciplines, for the provisioning of queues and link capacity, and for choosing parameters in simulation.

Computing and Informatics. Volume 23, 2004, No. 4: 317-335.

  An Application of Collaborative Web Browsing Based on Ontology Learning from User Activities on the Web

Collaborative web browsing, ontology learning, user modeling

With explosively increasing amount of information on the Web, users have been getting more bored to seek relevant information. Several studies have introduced adaptive approaches to recognizing personal interests. This paper proposes the collaborative Web browsing system that can support users to share knowledge with other users. Especially, we have focused on user interests extracted from their own activities related to bookmarks. A simple URL based bookmark is provided with semantic and structural information by the conceptualization based on ontology. In order to deal with the dynamic usage of bookmarks, ontology learning based on a hierarchical clustering method can be exploited. As a result of our experiments, about 53.1 % of the total time was saved during collaborative browsing for seeking the equivalent set of information, compared with single Web browsing. Finally, we demonstrate implementing an application of collaborative browsing system through sharing bookmark-associated activities.

Computing and Informatics. Volume 23, 2004, No. 4: 337-353.

  Stratified Grammar Systems with Simple and Dynamically Organized Strata

Society theory of mind, stratified grammar systems, simple systems

Stratified grammar systems have been introduced as a grammatical model of M. Minsky hypothesis concerning how the mind works. This grammatical model is a restricted model since it is assumed that the strata of the mind are ordered in a given linear ordering. In this paper, we consider stratified grammar systems with strata organized dynamically, according to the current sentential form to be written, to meet Minsky hypothesis that the strata of the mind are organized dynamically according to the current task to be processed. We study the generative power of these systems, which we shall call dynamic stratified grammar systems, and we show that they generate the family of matrix grammars. Also, we consider simple systems by limiting the number of components comprising the stratum to be at most two components with only one rule each. Then, we show that every dynamic stratified grammar system can be represented by an equivalent simple one which demonstrates the ideas of generating complicated behaviors through more or less coordinated activities of entities with simpler behaviors.

Computing and Informatics. Volume 23, 2004, No. 4: 355-362.

  Forwarding Based Data Parallel Handoff for Real-Time QoS in Mobile IPv6 Networks

Forwarding scheme, bandoff, Mobile IPv6, quality of service (QoS), routing

Real time mobile applications with guaranteed quality of service (QoS) are expected to be popular due to drastic increase of mobile Internet users. Many Resource ReSerVation Protocol (RSVP) based handover schemes in MIPv4 were studied in the literature for those services. However, the buffering overhead is unavoidable for the latency to optimize the route in new path establishment. Even though the data forwarding based schemes minimize the data loss and provide faster handoff, there are still some overheads when forwarding them and limitation on MIPv4. In this paper we propose a novel handoff scheme in MIPv6 based on forwarding which balances route traffic and reduces the overhead. The comprehensive performance evaluation shows that the disruption time and the signaling overhead are significantly reduced up to about 62 % and 73 % respectively, in comparison with well-known previous schemes discussed in cite{Low, Real}. Furthermore, it is able to transmit data with the reduced latency and guarantee the fast and secure seamless services.

Computing and Informatics. Volume 23, 2004, No. 4: 363-376.

  The Effects of Transfer of Global Improvements in Genetic Programming

Automatically defined functions, cultural evolution, co-evolution, genetic programming

Koza has shown how Automatically Defined Functions (ADFs) can reduce computational effort in the genetic programming paradigm. In Koza's Automatically Defined Functions, as well as in standard genetic programming, an improvement in a part of a program (an ADF or a main body) can only be transferred to other individuals in the population via crossover. In this article, we consider whether it is a good idea to transfer immediately improvements found by a single individual to other individuals in the population. A system that implements this idea has been proposed and tested for the even-5-parity, even-6-parity, and even-10-parity problems. Results are very encouraging: computational effort is reduced (compared to Koza's ADFs) and the system seems to be less prone to early stagnation. Also, as evolution occurs in separate populations, our approach permits to parallelize genetic programming in another different way.

Computing and Informatics. Volume 23, 2004, No. 4: 377-394.

  Service Negotiation Model for Response Time in Distributed Networks

Response time, specifying policies, negotiation

The important thing of QoS is that response time of service is transparently suggested to resource management system and network users. This helps to schedule jobs or guarantee the service level agreement. This paper proposes to specify a negotiation policy for response time of distributed network using network latency function. To monitor and manage service response time in distributed network, we identified the relationships between network/application performance and QoS parameters. We also provided the statistical analysis on mapping user level response time to application and network level parameters. To show the validation of the network latency function, we used the NS-2 network simulator and showed the efficiency of that function. Finally we suggested the negotiation of policy for response time of requested service.

Computing and Informatics. Volume 23, 2004, No. 4: 395-405.