S. Misbah Deen

Power Consumption-Based Server Selection Algorithms for Communication-Based Systems

We have to reduce the total electrical power consumption in information systems. In this paper, we consider communication based applications where a server transmits a large volume of data to a client like file transfer protocol (FTP). We discuss a power consumption model for communication-based applications, where the total power consumption of a server depends on the total transmission rate and number of clients where the server concurrently transmits files. A client has to select a server in a set of possible servers, each of which holds a file, so that the power consumption of the server is reduced. We evaluate a pair of PCB (power consumption-based) and TRB (transmission rate-based) algorithms to select a server. In the evaluation, we show the total power consumption can be reduced by the PCB and TRB algorithms compared with the traditional round-robin (RR) algorithm and PCB is more practical than TRB.

Fault‐tolerant holonic manufacturing systems

This paper presents a model of fault‐tolerant holonic manufacturing systems (HMS) where each holons activities are controlled by an intelligent software agent. Multiple agents schedule actions, resolve conflicts and manage information to produce, transport, assemble, inspect and store customized products. Our model provides robustness and distribution transparency across a shop‐floor where unpredictable failures occur with machines, control software and communication networks. Each autonomous holon is composed of a hierarchy of large‐grain functional components where interaction is carried out by user‐defined cooperation strategies. These strategies enable holons to coordinate their behaviour through exchanging messages and sensing/actuating of their shared environment. Therefore, holonic agents can select suitable rescheduling and recovery mechanisms to tolerate faults and keep the manufacturing system working. We also propose how the IEC 1499 standard (Function Block Architecture) for distributed control systems could be used to implement our model. The model presented here is a crystallization of some abstract concepts from a generic cooperating agent system, with suitable extensions to meet the criteria of the ongoing HMS project. Copyright

A Database Perspective to a Cooperation Environment

This paper will present the authors view of a Cooperating Knowledge Based System (CKBS) as an applied multi-agent system with a database perspective, based on well-defined computer-science concepts, rather than AI concepts. Each agent will be seen as an autonomous (necessarily large-grain) system which implicitly cooperates with other agents to achieve a global goal in a potentially multi-user environment, where performance, reliability, concurrent usage, user-friendliness are particularly important.

Flexible wide-area group communication protocols-international experiments

In distributed applications, a group of multiple processes is required to be cooperated by exchanging multimedia data. In addition, world-wide distributed applications are being realized by using the Internet. The traditional group communication protocols assume that every pair of processes support the same and fixed delay time and reliability level. In world-wide multimedia applications, the assumption does not hold. We discuss high-speed protocols which can change the way of distributing messages to multiple destinations and retransmitting messages to processes losing the messages in the wide-area group in the change of the delay and reliability. We present the evaluation of the protocols in the world-wide environment.

TBB-Scheme for Reliably Broadcast Messages among Peer Processes

Nowadays information systems are being shifted to distributed architectures to obtain the benefits like scalability, autonomy, and faulty-tolerance. The peer-to-peer (P2P) model as a fully distributed system, is composed of peer processes (peers) which cooperate with each other to achieve a common goal. Here, peers have to efficiently and flexibly make an agreement on one common value which satisfies an agreement condition. We use the multi-value exchange (MVE) scheme for efficiently making an agreement where each peer sends a package of multiple possible values to the other peers at ongoing rounds. In order to efficiently broadcast values in a group, we take advantage of the multipoint relaying (MPR) mechanism. Here, if a peer who forwards messages to other peers is faulty, the peers cannot receive messages. In this paper, we discuss a trustworthiness-based broadcast (TBB) scheme where only the trustworthy peers forward messages. That is, untrustworthy peers, i.e. peers prone to faults and malicious behaviors do not forward the messages. Here, the transmission fault implied by faults of untrustworthy peers can be reduced. We evaluated the TBB scheme in terms of the number of messages compared with the MPR one.

A Query Subsumption Technique

The paper examines query subsumptions in a relational context and develops a general subsumption technique for queries with function-free firstorder predicates. The predicates are compacted (removing redundant terms) and then expressed as of a disjunction of conjunctions without negations, which is then transformed into a canonical form, along with the rest of the query. Queries in this form are then checked for both result and attribute subsumptions. In the process it highlights some of the logical pitfalls and discusses how they are taken into account in the proposed technique. A filter is then used to derive the new query from the old one.

Hybrid Clock-Based Synchronization in a Scalable Heterogeneous Group

In peer-to-peer (P2P) applications, a group of multiple peer processes (peers) are required to cooperate with each other. In this paper, we discuss a heterogeneous hybrid time group communication (HHT) protocol which takes advantage of the linear time (LT) and physical time (PT) to causally order messages in a scalable heterogeneous group. It depends on accuracy of each physical clock and minimum delay time between a pair of peers how messages can be ordered. In this paper, we consider a heterogeneous type of group where the clock accuracy of each peer and the minimum delay time between every pair of peers are not the same. In group protocols, even if a pair of messages are ordered in the protocol, the messages may not be causally ordered. Thus, some messages are unnecessarily ordered in the protocols. In this paper, we show the number of messages to be unnecessarily ordered can be reduced in the HHT protocol. In a scalable group, it is not easy, maybe impossible for each peer to hold information on the clock accuracy and minimum delay time of every peer. In this paper, we newly consider a two-layered model of a heterogeneous group to reduce the information which each peer has to hold.

A general framework for coherence in a CKBS

Coherence in a distributed system is meant to offset the disadvantages of distribution. The paper explores four issues under coherence, namely preservation of knowledge consistency across the agents, reliability of the overall system, integration of local solutions and the global performance. It presents some general strategies that can be employed to improve coherence in a CKBS, which include a weak consistency with versions for knowledge revision, and a recovery mechanism based on a hierarchic three-stage coordination, which ensures the correct isolation of potentially hierarchic multiagent actions. The paper goes on to identify the sources and classes of conflicts in global integration, and it suggests remedies, which at worst case would involve negotiation. In global performance, it focusses on planning and result synthesis, as the two most important problem domains, and suggests strategies ameliorate performance.

The Delay Time-Based (DTB) Algorithm for Energy-Efficient Server Cluster Systems

The improved power consumption laxity-based (IPCLB) algorithm is discussed to select one of servers so that the total power consumption of a cluster can be reduced. However, a load balancer has to collect a state of every current process on servers of a cluster to calculate the estimated power consumption of each server. In addition, it is difficult to precisely estimate the power consumption of each server since the state of each process on the server is changed during the estimation. Especially, a process might terminate before the termination time is estimated if the computation time of the process is shorter than the communication delay time between the load balancer and the server. In this paper, we assume the computation time of each process is shorter than the communication delay time. Then, we propose a delay time-based (DTB) algorithm to select a server for each request process so that the total power consumption of a cluster to perform processes on the server can be reduced. In the DTB algorithm, it is not necessary to collect a state of every process on each server to estimate the power consumption laxity. In addition, the minimum computation time of a process is not required to be a priori defined in the DTB algorithm.

Cooperating Agents for Holonic Manufacturing

In a Cooperating Knowledge Based System (CKBS) an agent is modelled as an autonomous and cooperative knowledge based system, capable of executing some tasks in the most effective way, using an engineering paradigm. The paper presents an abstract CKBS model, using Holonic Manufacturing Systems (HMS) as an application domain. HMS is a major international project on agent-based manufacturing, where a holon is a unit of production and is a type of agent, cooperating with other agents in task sharing. This paper describes a highly distributed architecture of the model (designed to provide systems robustness and fault-tolerance) and the necessary computational model required to ensure the correct systems behaviour.