45,534 research outputs found
Challenges to describe QoS requirements for web services quality prediction to support web services interoperability in electronic commerce
Quality of service (QoS) is significant and necessary for web service applications quality assurance. Furthermore, web services quality has contributed to the successful implementation of Electronic Commerce (EC) applications. However, QoS is still the big issue for web services research and remains one of the main research questions that need to be explored. We believe that QoS should not only be measured but should also be predicted during the development and implementation stages. However, there are challenges and constraints to determine and choose QoS requirements for high quality web services. Therefore, this paper highlights the challenges for the QoS requirements prediction as they are not easy to identify. Moreover, there are many different perspectives and purposes of web services, and various prediction techniques to describe QoS requirements. Additionally, the paper introduces a metamodel as a concept of what makes a good web service
QoS-Aware Middleware for Web Services Composition
The paradigmatic shift from a Web of manual interactions to a Web of programmatic interactions driven by Web services is creating unprecedented opportunities for the formation of online Business-to-Business (B2B) collaborations. In particular, the creation of value-added services by composition of existing ones is gaining a significant momentum. Since many available Web services provide overlapping or identical functionality, albeit with different Quality of Service (QoS), a choice needs to be made to determine which services are to participate in a given composite service. This paper presents a middleware platform which addresses the issue of selecting Web services for the purpose of their composition in a way that maximizes user satisfaction expressed as utility functions over QoS attributes, while satisfying the constraints set by the user and by the structure of the composite service. Two selection approaches are described and compared: one based on local (task-level) selection of services and the other based on global allocation of tasks to services using integer programming
Bipolar Proof Nets for MALL
In this work we present a computation paradigm based on a concurrent and
incremental construction of proof nets (de-sequentialized or graphical proofs)
of the pure multiplicative and additive fragment of Linear Logic, a resources
conscious refinement of Classical Logic. Moreover, we set a correspon- dence
between this paradigm and those more pragmatic ones inspired to transactional
or distributed systems. In particular we show that the construction of additive
proof nets can be interpreted as a model for super-ACID (or co-operative)
transactions over distributed transactional systems (typi- cally,
multi-databases).Comment: Proceedings of the "Proof, Computation, Complexity" International
Workshop, 17-18 August 2012, University of Copenhagen, Denmar
A front-end system to support cloud-based manufacturing of customised products
In today’s global market, customized products are amongst an important means to address diverse customer demand and in achieving a unique competitive advantage. Key enablers of this approach are existing product configuration and supporting IT-based manufacturing systems. As a proposed advancement, it considered that the development of a front-end system with a next level of integration to a cloud-based manufacturing infrastructure is able to better support the specification and on-demand manufacture of customized products. In this paper, a new paradigm of Manufacturing-as-a-Service (MaaS) environment is introduced and highlights the current research challenges in the configuration of customizable products. Furthermore, the latest development of the front-end system is reported with a view towards further work in the research
MDCC: Multi-Data Center Consistency
Replicating data across multiple data centers not only allows moving the data
closer to the user and, thus, reduces latency for applications, but also
increases the availability in the event of a data center failure. Therefore, it
is not surprising that companies like Google, Yahoo, and Netflix already
replicate user data across geographically different regions.
However, replication across data centers is expensive. Inter-data center
network delays are in the hundreds of milliseconds and vary significantly.
Synchronous wide-area replication is therefore considered to be unfeasible with
strong consistency and current solutions either settle for asynchronous
replication which implies the risk of losing data in the event of failures,
restrict consistency to small partitions, or give up consistency entirely. With
MDCC (Multi-Data Center Consistency), we describe the first optimistic commit
protocol, that does not require a master or partitioning, and is strongly
consistent at a cost similar to eventually consistent protocols. MDCC can
commit transactions in a single round-trip across data centers in the normal
operational case. We further propose a new programming model which empowers the
application developer to handle longer and unpredictable latencies caused by
inter-data center communication. Our evaluation using the TPC-W benchmark with
MDCC deployed across 5 geographically diverse data centers shows that MDCC is
able to achieve throughput and latency similar to eventually consistent quorum
protocols and that MDCC is able to sustain a data center outage without a
significant impact on response times while guaranteeing strong consistency
Systematic composition of distributed objects: Processes and sessions
We consider a system with the infrastructure for the creation and interconnection of large numbers of distributed persistent objects. This system is exemplified by the Internet: potentially, every appliance and document on the Internet has both persistent state and the ability to interact with large numbers of other appliances and documents on the Internet. This paper elucidates the characteristics of such a system, and proposes the compositional requirements of its corresponding infrastructure. We explore the problems of specifying, composing, reasoning about and implementing applications in such a system. A specific concern of our research is developing the infrastructure to support structuring distributed applications by using sequential, choice and parallel composition, in the anarchic environment where application compositions may be unforeseeable and interactions may be unknown prior to actually occurring. The structuring concepts discussed are relevant to a wide range of distributed applications; our implementation is illustrated with collaborative Java processes interacting over the Internet, but the methodology provided can be applied independent of specific platforms
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