Concurrent Services Research Articles

One Patient, 2 Physicians

Reporting concurrent care services based on the respective level of care performed by 2 or more physicians for the same patient

Establishing composite SLAs through concurrent QoS negotiation with surplus redistribution

SUMMARYThe end‐to‐end QoS negotiation for service level agreement establishment for composite services involves compound multi‐party negotiations in which the composite service provider concurrently negotiates with multiple candidates for each atomic service, selecting the one that best satisfies the atomic service QoS preferences while ensuring that the end‐to‐end QoS requirements are also fulfilled. In order to be able to negotiate with potential candidates, it is necessary to derive the atomic utility boundaries from the global utility boundary. Additionally, there has to be a mechanism for updating these boundaries in subsequent negotiation rounds based on the individual negotiation outcomes. In this paper, we propose an algorithm for the decomposition of global utility boundary into atomic service utility boundaries, and the surplus redistribution from successful negotiation outcomes among the remaining negotiations. The proposed mechanism is a practical approach to efficiently coordinate concurrent service negotiations within complex workflows, enabling the iterative and interactive adjustment of the negotiation boundaries for each atomic service in a composition based on the performance of other atomic negotiations. We demonstrate the feasibility of our approach by evaluating it with some popular negotiation strategies using the Specialized Property Search Scenario. Copyright © 2011 John Wiley & Sons, Ltd.

Cause-effect relationships and the service quality evaluation criteria of portal sites

Evaluation of portal site service quality is relatively important for concurrent web services today. The practitioners and academicians are utilizing all kinds of tools to figure out what are the criteria presented as benchmark for portal website service quality. This study uses literature review to attribute the twenty-two portal site service quality evaluation criteria to compose the survey instrument. The hierarchical random sampling method is manipulated in this study. This study collected 1320 valid instruments from the large online population and university students. The decision making trial and evaluation laboratory method applied to compose a cause and effect model to examine the customer expectations of the portal site service quality. The results and managerial implications are discussed.

GA optimization of Petri net-modeled concurrent service systems

This paper deals with the performance modeling and the optimization of concurrent service systems. In large and complex service systems, asynchronous and concurrently occurring activities are common. Petri nets are ideal tools for modeling concurrent systems. However, Petri nets are lacking in time duration concept, in data collecting mechanism and in conjunctive logic on the preconditions of an event. These inherent limitations along with the state explosion problem severely restrict their scope of application. In this paper, we introduce the Client Server Petri net, which overcomes all these limitations. The Client Server Petri net is an extension of the Generalized Stochastic Petri net that allows greater flexibility in modeling and simulating concurrent systems. The total operational cost of service systems consists of service cost and waiting cost. The former is due to the hiring of service personnel, while the latter is due to the fact that customers weary of waiting may take their business somewhere else. The problem, in principle, can be formulated as a multi-objective optimization problem and then solved to obtain the Pareto-front. In this study, however, we formulate it as a single-objective optimization problem because optimization (minimization) of the total cost (service cost + waiting cost) is of paramount importance in economic models. Finding the optimal operational cost becomes a combinatorial optimization problem which we seek to minimize using the genetic algorithm, known for its robustness and versatility as an optimization meta-heuristic. We demonstrate the effectiveness of the novel Client Server Petri net model editor–simulator–optimizer with the practical example of an automobile purchase concurrent service system.

TESTQUAL: Conceptualizing Software Testing as a Service

Software testing has emerged as a distinct and critical component in software development. This paper argues that software testing should be conceptualized as a concurrent service throughout the software development process rather than being viewed as a sequential line of responsibility. Testing as a service has two key aspects: (1) a service to developers, and (2) a service to end users. This paper draws from the service quality and SERVQUAL literature to propose a structured measurement tool for testing as a service. Software quality is the most prominent outcome for TESTQUAL. The potential antecedents and outcomes of TESTQUAL are briefly discussed. The implications to research and practice of TESTQUAL are also discussed.

Customer interaction in service innovation: seldom intensive but often decisive. Case studies in three business service sectors

The purpose of this study was to develop the yet limited empirical knowledge on the intensity of customer interaction and on specific customer roles in service innovation processes. An empirical study of 12 business service innovation projects was conducted in cleaning and security, financial, and ICT services. Overall, direct customer interaction in service development can be characterised as being limited and focused on specific, well-defined tasks in these service sectors, which offer support services to their customers. In the analysis, three highly important customer roles emerged: 1 customers act as catalysts of service development processes 2 customer feedback is often decisive in nature, allowing for go/kill decisions and directing other key decisions 3 customers have a key role in internal marketing of the new service idea within the provider organisation. The study also proposes a new variant of a concurrent service innovation process to existing service innovation literature.

A Petri Net-based approach for data race detection in BPEL

As more and more workflows modeled using business process execution language (BPEL), there is a strong demand on the reliability of BPEL program. However, the current BPEL specification does not include the reliability as a feature. As a semiformal flow-based language, data race is a serious problem in BPEL. In order to validate the data race problem, we first transform a BPEL program into Concurrency Service Workflow net (CSW_net). Based on this formalism, we propose a happens-before based approach to analyze the data race problem. Our approach considered the time character of BPEL to enhance recall rate of data race detection. Our approach is validated through a use case and further research directions are pointed out at last.

OFDMA-based LAN emulation in long-reach hybrid PON system

A novel long-reach, hybrid wavelength-division multiplexing (WDM) and time-division multiplexing (TDM) passive optical network (PON) architecture which supports local area network (LAN) emulation among customers is proposed. Orthogonal frequency division multiplexing access (OFDMA) technology is used in optical network units (ONUs) to transmit the LAN data. The optical LAN data from an ONU is converted into the electrical signal and combined with TDM downstream access data in the extended box for delivery to other ONUs. This scheme has many advantages on LAN emulation, such as dynamic allocation of LAN bandwidth, no bandwidth cost of TDM business, supporting multiple concurrent LAN services and so on. Simulations are performed to verify the scheme. Tolerance of dispersion and factors that influence the performance of various independent services are all investigated and analyzed.

TRainbow: a new trusted virtual machine based platform

Currently, with the evolution of virtualization technology, cloud computing mode has become more and more popular. However, people still concern the issues of the runtime integrity and data security of cloud computing platform, as well as the service efficiency on such computing platform. At the same time, according to our knowledge, the design theory of the trusted virtual computing environment and its core system software for such network-based computing platform is at the exploratory stage. In this paper, we believe that efficiency and isolation are the two key proprieties of the trusted virtual computing environment. To guarantee these two proprieties, based on the design principle of splitting, customizing, reconstructing, and isolation-based enhancing to the platform, we introduce TRainbow, a novel trusted virtual computing platform developing by our research group.With the two creative mechanisms, that is, capacity flowing amongst VMs and VM-based kernel reconstructing, TRainbow provides great improvements (up to 42%) in service performance and isolated reliable computing environment for Internet-oriented, large-scale, concurrent services.

DoS Attacks on Real-Time Media through Indirect Contention-in-Hosts

Quality of service (QoS) is critical for delivering real-time media services (RTMSs). The authors identify a new class of denial-of-service attacks against RTMSs - indirect contention-in-hosts (ICiH). Here, attackers attempt to indirectly degrade RTMS QoS by directing packets at other concurrent services, thereby inducing resource contention between RTMS packets and attack packets in the protocol stack. To analyze such attacks, the authors' operation-trace analysis method formalizes the notion of contention among concurrent services and develops several metrics to quantify ICiH's effects.

Study on the account-sharing strategy for multi-services in IMS online charging mechanism

A prepaid subscriber is allowed to simultaneously implement multiple services in online charging mechanism of IP Multimedia Subsystem (IMS). It is a noteworthy discussion to effectively distribute the limited account resources among concurrent services. An account-sharing algorithm is proposed for multi-services, which introduces resource reclamation and redistribution processes based on the resource reservation of standard specifications and dynamically adjusts them according to the changes of Quality of Service (QoS). Three performance indexes are investigated in the simulation experiments, which are average number of accommodated sessions, average number of completed sessions, and average number of iterations per accommodated session. The results show that in the normal QoS level, the three indexes of the proposed algorithm averagely increase by 18.7%, 5.4%, and 3.1% compared with the Prepaid Credit Distribution (PCD) algorithm, and by 2.1%, 1.0%, and 1.8% compared with the Prepaid Credit Reclaim (PCR) algorithm. In the poor QoS level, the performance advantages are greater, which averagely increase by 29.1%, 7.1%, and 2.8% compared with PCD, and by 9.4%, 4.1%, and 3.6% compared with PCR.

Trust or Profit: An Examination of Whether Military Officers May Serve as Members of Congress or Presidential Electors

This paper examines the ability of reserve and active duty military officers to serve in certain political offices, such as Congress and the Electoral College. The seminal case on this issue, U.S. v. Lane, dealt with a U.S. senator who served as a reserve military judge. In deciding the case, the Court of Appeals for the Armed Forces only stated that a member of Congress may not also serve as a judge, but did not reach the ultimate issue of concurrent military service. This paper will attempt to show in exactly which political offices military officers may serve. In making its determinations, this paper examines the Constitution, case law, statutes, legislative history, and federal regulations.

Performance study of data layout schemes for a SAN-based video server

We describe the design and performance of storage area network multimedia server (SAM), which manages a set of parallel storage devices connected by a storage area network. SAM is geared towards providing multiple concurrent services such as interactive video-on-demand and video games. The challenge, therefore, is twofold: provide a high throughput in order to service the maximum number of users possible, with a small response time that is necessary for interactive applications. The primary focus of this paper is on the data layout scheme for SAM. The problem of out-of-order delivery of video frames is described, and a scheme to transmit the frames in order is presented. A data layout scheme called constrained random striping (CRS) is developed for the logical loop model. Using a simulation model, the performance of this scheme is compared with several other data layout strategies. It is shown that CRS reduces the start-up latency of clients. The performance gains and tradeoffs of the different strategies are discussed in detail.

Optimization of Concurrent Service Systems Under Fuzzy Constraints

Optimization of Concurrent Service Systems Under Fuzzy Constraints

PERFORMANCE MODELS FOR STUDYING AND ANALYZING REAL-TIME MULTIMEDIA SYSTEMS

As real-time systems continue to grow, performance evaluation plays a critical role in the design of these systems since the computation time, the service time, and the responsive actions must satisfy the time constraints. One of these systems is the real-time distributed multimedia-on-demand (MOD) service system. The MOD system usually fails when it misses a task deadline. The main units of the MOD system usually communicate with each other and work concurrently under timing constraints. The MOD system is designed to store, retrieve, schedule, synchronize and communicate objects comprising of mixed data types including images, text, video and audio, in real-time. In the MOD system, such data types represent the main concept of movie files. Modeling of such concurrency, communication, timing, and multimedia service (e.g., store, retrieve) is essential for evaluating the real-time MOD system. To illustrate how to model and analyze the important multimedia aspects of the MOD system, we use the Real-net (R-net) modeling technique. We choose R-net as an extension of Time Petri Net due to its ability to specify hard real-time process interaction, represent the synchronization of multimedia entities, describe concurrent multimedia activities, and illustrate the inter-process timing relationships as required for multimedia presentation. Based on modular techniques, we build three R-net performance models for describing the dynamic behavior of the MOD service system. The first model adopts the Earliest Deadline First (EDF) disk scheduling algorithm. The other models adopt the Scan-EDF algorithm. These algorithms help us to illustrate how the real-time user requests can be satisfied within the specified deadline times. Since R-nets are amenable to analysis including Markov process modeling, the interesting performance measures of the MOD service system such as the quality of service, the request response time, the disk scheduling algorithm time, and the actual retrieval time can be easily computed. In the performance analysis of the MOD models, we use our R-NET package.

Unraveling the Puzzle: Critical Care, Intensive Care, or an Evaluation and Management Visit Code?

Unraveling the Puzzle: Critical Care, Intensive Care, or an Evaluation and Management Visit Code?

Concurrent data transmission through analog speech channel using data hiding

In this letter, we propose to perform concurrent data transmissions through analog speech channels using a data hiding technique. In particular, concurrent data are modulated into a noise-like signal and imperceptibly embedded into voices. Conventional embedding methods usually treat speech as a source of interferences to the simultaneously transmitted data. The proposed scheme exploits the knowledge of the speech signal during embedding. Therefore, such an interference can be effectively removed, and a higher data rate can be achieved. Besides, the proposed scheme is compatible with conventional phone terminals. A conventional telephone set is still able to access the basic voice service, while the added decoding mechanism can extract the embedded data and provide various concurrent services. The performance of the proposed method is analyzed. Experimental results demonstrate that an acceptable data rate and bit-error rate can be achieved.

Advanced RF/Baseband Interconnect Schemes for Inter- and Intra-ULSI Communications

Future inter- and intra-ULSI interconnect systems demand extremely high data rates (up to 100 Gbps/pin or 20-Tbps aggregate) as well as bidirectional multiI/O concurrent service, re-configurable computing/processing architecture, and total compatibility with mainstream silicon system-on-chip and system-in-package technologies. In this paper, we review recent advances in interconnect schemes that promise to meet all of the above system requirements. Unlike traditional wired interconnects based solely on time-division multiple access for data transmission, these new interconnect schemes facilitate the use of additional multiple access techniques including code-division multiple access and frequency-division multiple access to greatly increase bandwidth and channel concurrency as well as to reduce channel latency. The physical transmission line is no longer limited to a direct-coupled metal wire. Rather, it can be accomplished via either wired or wireless mediums through capacitor couplers that reduce the baseband noise and dc power consumption while simplifying the fabrication process by eliminating vertical metal studs needed in three-dimensional ICs. These new advances in interconnect schemes would fundamentally alter the paradigm of ULSI data communications and enable the design of next-generation computing/processing systems.

Modeling Concurrent, Sequential, Storage, Retrieval, and Scheduling Activities of Multimedia Systems

As real-time systems continue to grow, performance evaluation plays a critical role in the design of these systems since the computation time, the service time, and the responsive actions must satisfy the time constraints. One of these systems is the real-time distributed multimedia-on-demand (MOD) service system. The MOD system usually fails when it misses a task deadline. The main units of the MOD system usually communicate with each other and work concurrently under timing constraints. The MOD system is designed to store, retrieve, schedule, synchronize, and communicate objects comprised of mixed data types including images, text, video, and audio, in real-time. In the MOD system, such data types represent the main concept of movie files. Modeling of such concurrency, communication, timing, and multimedia service (e.g. store, retrieve) is essential for evaluating the real-time MOD system. To illustrate how to model and analyze the important multimedia aspects of the MOD system, we use the Real-net (R-net) modeling technique. We choose R-net as an extension of Time Petri Net due to its ability to specify hard real-time process interaction, represent the synchronization of multimedia entities, describe concurrent multimedia activities, and illustrate the inter-process timing relationships as required for multimedia presentation. Based on modular techniques, we build three R-net performance models for describing the dynamic behavior of the MOD service system. The first model adopts the Earliest Deadline First (EDF) disk scheduling algorithm. The other models adopt the Scan-EDF algorithm. These algorithms help us to illustrate how the real-time user requests can be satisfied within the specified deadline times. Since R-nets are amenable to analysis including Markov process modeling, the interesting performance measures of the MOD service system such as the quality of service, the request response time, the disk scheduling algorithm time, and the actual retrieval time can be easily computed. In the performance analysis of the MOD models, we use our R-NET package.

Scalable hierarchical locking for distributed systems

Middleware components are becoming increasingly important as applications share computational resources in distributed environments, such as high-end clusters with ever larger number of processors, computational grids and increasingly large server farms. One of the main challenges in such environments is to achieve scalability of synchronization. In general, concurrency services arbitrate resource requests in distributed systems. But concurrency protocols currently lack scalability. Adding such guarantees enables resource sharing and computing with distributed objects in systems with a large number of nodes. The objective of our work is to enhance middleware services to provide scalability of synchronization and to support state replication in distributed systems. We have designed and implemented a middleware protocol in support of these objectives. Its essence is a peer-to-peer protocol for multi-mode hierarchical locking, which is applicable to transaction-style processing and distributed agreement. We demonstrate high scalability combined with low response times in high-performance cluster environments. Our technical contribution is a novel, fully decentralized, hierarchical locking protocol to enhance concurrency in distributed resource allocation following the specification of general concurrency services for large-scale data and object repositories. Our experiments on an IBM SP show that the number of messages approaches an asymptote at 15 node from which point on the message overhead is in the order of 3–9 messages per request, depending on system parameters. At the same time, response times increase linearly with a proportional increase in requests and, consequently, higher concurrency levels. Specifically, in the range of up to 80 nodes, response times under 10 ms are observed for critical sections that are one 25th the size of non-critical code. The high degree of scalability and responsiveness of our protocol is due in large to a high level of concurrency upon resolving requests combined with dynamic path compression for request propagation paths. Our approach is not only applicable to CORBA, its principles are shown to provide benefits to general distributed concurrency services and transaction models. Besides its technical strengths, our approach is intriguing due to its simplicity and its wide applicability, ranging from large-scale clusters to server-style computing.