1,963 research outputs found
A Methodology for Engineering Collaborative and ad-hoc Mobile Applications using SyD Middleware
Today’s web applications are more collaborative and utilize standard and ubiquitous Internet protocols. We have earlier developed System on Mobile Devices (SyD) middleware to rapidly develop and deploy collaborative applications over heterogeneous and possibly mobile devices hosting web objects. In this paper, we present the software engineering methodology for developing SyD-enabled web applications and illustrate it through a case study on two representative applications: (i) a calendar of meeting application, which is a collaborative application and (ii) a travel application which is an ad-hoc collaborative application. SyD-enabled web objects allow us to create a collaborative application rapidly with limited coding effort. In this case study, the modular software architecture allowed us to hide the inherent heterogeneity among devices, data stores, and networks by presenting a uniform and persistent object view of mobile objects interacting through XML/SOAP requests and responses. The performance results we obtained show that the application scales well as we increase the group size and adapts well within the constraints of mobile devices
Many Server Scaling of the N-System Under FCFS-ALIS
The N-System with independent Poisson arrivals and exponential
server-dependent service times under first come first served and assign to
longest idle server policy has explicit steady state distribution. We scale the
arrival and the number of servers simultaneously, and obtain the fluid and
central limit approximation for the steady state. This is the first step
towards exploring the many server scaling limit behavior of general parallel
service systems
InterCloud: Utility-Oriented Federation of Cloud Computing Environments for Scaling of Application Services
Cloud computing providers have setup several data centers at different
geographical locations over the Internet in order to optimally serve needs of
their customers around the world. However, existing systems do not support
mechanisms and policies for dynamically coordinating load distribution among
different Cloud-based data centers in order to determine optimal location for
hosting application services to achieve reasonable QoS levels. Further, the
Cloud computing providers are unable to predict geographic distribution of
users consuming their services, hence the load coordination must happen
automatically, and distribution of services must change in response to changes
in the load. To counter this problem, we advocate creation of federated Cloud
computing environment (InterCloud) that facilitates just-in-time,
opportunistic, and scalable provisioning of application services, consistently
achieving QoS targets under variable workload, resource and network conditions.
The overall goal is to create a computing environment that supports dynamic
expansion or contraction of capabilities (VMs, services, storage, and database)
for handling sudden variations in service demands.
This paper presents vision, challenges, and architectural elements of
InterCloud for utility-oriented federation of Cloud computing environments. The
proposed InterCloud environment supports scaling of applications across
multiple vendor clouds. We have validated our approach by conducting a set of
rigorous performance evaluation study using the CloudSim toolkit. The results
demonstrate that federated Cloud computing model has immense potential as it
offers significant performance gains as regards to response time and cost
saving under dynamic workload scenarios.Comment: 20 pages, 4 figures, 3 tables, conference pape
Continuous time control of make-to-stock production systems
Ankara : The Department of Industrial Engineering and the Institute of Engineering and Sciences of Bilkent University, 2010.Thesis (Ph. D.) -- Bilkent University, 2010.Includes bibliographical references leaves 117-120.We consider the problem of production control and stock rationing in a make-tostock
production system with multiple servers –parallel production channels--, and
several customer classes that generate independent Poisson demands. At decision
epochs, in conjunction with the stock allocation decision, the control specifies
whether to increase the number of operational servers or not. Previously placed
production orders cannot be cancelled. We both study the cases of exponential and
Erlangian processing times and model the respective systems as M /M /s and M /Ek /s
make-to-stock queues. We characterize properties of the optimal cost function, and
of the optimal production and rationing policies. We show that the optimal
production policy is a state-dependent base-stock policy, and the optimal rationing
policy is of state-dependent threshold type. For the M /M /s model, we also prove
that the optimal ordering policy transforms into a bang-bang type policy when we
relax the model by allowing order cancellations. Another model with partial ordercancellation
flexibility is provided to fill the gap between the no-flexibility and the
full-flexibility models. Furthermore, we propose a dynamic rationing policy for the
systems with uncapacitated replenishment channels, i.e., exogenous supply systems. Such systems can be modeled by letting s --the number of replenishment channels--
go to infinity. The proposed policy utilizes the information on the status of the
outstanding replenishment orders.
This work constitutes a significant extension of the literature in the area of control
of make-to-stock queues, which considers only a single server. We consider an
arbitrary number of servers that makes it possible to cover the spectrum of the cases
from the single server to the infinite servers. Hence, our work achieves to analyze
both the exogenous and endogenous supply leadtimes.Bulut, Ă–nderPh.D
Actors that Unify Threads and Events
There is an impedance mismatch between message-passing concurrency and virtual machines, such as the JVM. VMs usually map their threads to heavyweight OS processes. Without a lightweight process abstraction, users are often forced to write parts of concurrent applications in an event-driven style which obscures control flow, and increases the burden on the programmer. In this paper we show how thread-based and event-based programming can be unified under a single actor abstraction. Using advanced abstraction mechanisms of the Scala programming language, we implemented our approach on unmodified JVMs. Our programming model integrates well with the threading model of the underlying VM
Advance reservation games
Advance reservation (AR) services form a pillar of several branches of the economy, including transportation,
lodging, dining, and, more recently, cloud computing. In this work, we use game theory to analyze a slotted
AR system in which customers differ in their lead times. For each given time slot, the number of customers
requesting service is a random variable following a general probability distribution. Based on statistical
information, the customers decide whether or not to make an advance reservation of server resources in
future slots for a fee. We prove that only two types of equilibria are possible: either none of the customers
makes AR or only customers with lead time greater than some threshold make AR. Our analysis further
shows that the fee that maximizes the provider’s profit may lead to other equilibria, one of which yields zero
profit. In order to prevent ending up with no profit, the provider can elect to advertise a lower fee yielding
a guaranteed but smaller profit. We refer to the ratio of the maximum possible profit to the maximum
guaranteed profit as the price of conservatism. When the number of customers is a Poisson random variable, we prove that the price of conservatism is one in the single-server case, but can be arbitrarily high in a many-server system.CNS-1117160 - National Science Foundationhttp://people.bu.edu/staro/ACM_ToMPECS_AR.pdfAccepted manuscrip
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