A Proactive Solution to Manage Web Service Unavailability in Service Oriented Software Systems

Towards a context-based multi-type policy approach for Web services composition

We identify parameters impacting Web services dependability, describe the methods of dependability enhancement by redundancy in space and redundancy in time, and perform a series of experiments to evaluate the availability of Web services. To increase the availability of Web services, we employ several replication schemes and compare them with a single service. The Web services are coordinated by a replication manager. It provides a round robin algorithm for scheduling the workload of the Web services and keeps updating the availability of each Web service. The replication algorithm and the detailed system configuration are described. Experiments are performed to evaluate the resulting service availability. Modeling on the Web services with Petri-net is constructed and verified through experiments with different applications. With the parameters obtained from the experiments, the proposed model can be engaged to demonstrate the characteristics of the Web service.

The recent approaches for Web services composition tend to integrate heterogeneous business processes executed in Peer-to-Peer networks. In such networks, component Web services are invoked on independent peers and are orchestrated according to the transactional requirements defined by the designers or the users of the composite Web service. Since component Web services can be dynamically invoked and are generally implemented as black boxes, concurrency between them may appear. This paper presents the transactional execution model of composite Web services exploiting the transactional properties of their component Web services. The proposed concurrency control is ensured by a decentralized serialization graph based on an optimistic protocol and on the hierarchical structure of the composition. The globally correct execution of the composite Web service is achieved by communication among dependent subtrans-actions and the peers they have accessed.

— This paper presents a framework for specifying Web services communities. A Web service is an accessible application that humans, software agents, and other applications in general can discover, compose, and invoke in order to satisfy users ’ needs like hotel booking. Web services providing the same functionality are gathered into one community, independently of their origins. This framework shows how software agents that are able to argue, negotiate, and reason about Web services can be used to specify these Web services and to manage their respective communities. The use of what we call argumentative agents helps Web services in being better organized within communities and in achieving the goals for which they are conceived. The community is led by a master component, which among others attracts new Web services to the community, retains existing Web services in the community, and identifies the Web services in the community that will participate in composite Web services. All these operations are managed by interacting agents through flexible conversations made up by argumentation, persuasion, and negotiation phases called dialogue games. I.

The essential services such as banking, transportation, medicine, education and defense are being progressively replaced by cheaper and more efficient Internet-based web applications. Therefore, the availability of web services is very critical for the socio-economic growth of the society. Distributed denial-of-service (DDoS) attacks pose an immense threat to the availability of these services. The services are severely degraded and hence lot of business loses are incurred due to these attacks. To objectively evaluate DDoS attack's impact, its severity and the effectiveness of a potential defense, we need precise, quantitative and comprehensive DDoS impact metrics that are applicable to web services. In this paper an attempt has been made to analyze impact of DDoS attacks on the web services. The experiments are conducted in NS-2. The attack traffic is mixed with legitimate traffic at different strengths and impact of DDoS attacks are measured in terms of throughput, response time, ratio of average serve to request rate, percentage link utilization, and normal packet survival ratio (NPSR). electronic document is a live template. The various components of your paper [title, text, heads, etc.] are already defined on the style sheet, as illustrated by the portions given in this document.

The emergence of the Sensor Web has paved the way for a new set of innovative software applications that exploit the enhanced availability of real‐time information. This article describes one such application built from Sensor Web components that aggregates GPS track data from a fleet of vehicles to provide an overview of road traffic congestion at the city scale. The application embodies a Service Oriented Architecture; web service components are used to archive and pre‐process incoming sensor observations, to encapsulate a horizontally partitioned spatial database that performs geoprocessing, and to disseminate results to client applications. Our results confirm that floating car data can provide an accurate depiction of current road traffic conditions. The presented solution uses Open Geospatial Consortium web services where possible and serves to highlight the difficulties inherent in achieving horizontal database scalability in sensor based geoprocessing systems.

Internet and Mobile technologies have greatly changed our lives in the past decade. However, the power and patentlals of the cambined capabilities offered by these two major inventions remain untapped. This paper looks into how we can turn these capabilities into service components that can be assembled into various composite services and enable people to have a simple way to enjoy camprehensive services anytime, anywhere, anyway with user and context relevance. We will explain in this paper how Web Services technologies and Service Oriented Architecture enables rapidly service creation; and the power of combining web technologies and mobile capabilities for service execution. Tourism is ane vertical industry chosen to apply this Service Provisioning concept. A packaged tour prototype is built to demonstrate the creation and execution of various tour services. These packaged tour services inciude both web and mobile service components and are described in service logic. Utilising the published services co...

Web services are increasingly used to enable interoperability and flexible integration of e-business systems. In this paper we focus on measurement-based performance analysis of an e-commerce application which uses Web services components to execute business operations. In our experiments we use a session-oriented workload generated by a tool developed accordingly to the TPC-W specification. The empirical results are obtained for two different user profiles, Browsing and Ordering, under different workload intensities. Unlike the previous work which was focused on the overall server response time and throughput, we present Web interaction, software architecture, and hardware resource level analysis of the system performance. In particular, we propose a method for extracting component level response times from the application server logs and study the impact of Web services and other components on the server performance. The results show that the response times of Web services components increase significantly under higher workload intensities when compared to other components. From the hardware resource measurements it is obvious that the higher response times of Web services components are due to parsing XML messages and contention for database resources. The results of our study identify software components and hardware resources which are potential bottlenecks in the system and thus provide valuable information for capacity planning of e-commerce applications

Web service adaptation is an important feature for mission critical Web services. It is widely recognized that thrashing and crashes occur in system saturation for many statically adaptive resource management algorithms, including CPU, memory, and network congestion. Service adaptation supports alternative responses to saturation control, maintaining service and server system stability and progress, instead of thrashing. In this paper, we present a design framework for developing adaptive web services. The core of this framework is the adaptation space model, which is based on the concepts of adaptation space and adaptation case. An adaptation space is defined by a use context and a partial order of adaptation cases. Each adaptation case describes a specific adaptation of a program or component of a web service. There are three main thrusts of the adaptation space approach. First, it defines a multi-dimensional adaptation context for capturing and coordinating different kinds of adaptation at different levels of a web service. Second, it provides a uniform way for representing and viewing a collection of alternative adaptations for a given web service component. Third, it promotes a declarative and incremental approach to adaptation specification, allowing the incorporation of new adaptation behavior of a web service in terms of existing adaptation cases. We evaluate the adaptation space approach using Ginga, an adaptive query processing service for handling queries over multiple data sources with diverse capabilities across the Internet. Our experimental results show that Ginga query adaptation can achieve significant performance improvements (up to 40% of response time gain) for processing distributed queries over the Internet in the presence of end-to-end delays.

As the amount of pathway information for various organisms is increasing very rapidly, performing various analyses on the full network of pathways for even multiple organisms can be possible and therefore developing an integrated database for storing and analyzing pathway information is becoming a critical issue. Until now analyzing these networks is not easy because of the nature of the existing pathway databases, which are often heterogeneous, incomplete, and/or inconsistent. We presented a database system called SPDBS to solve this problem. However, application-oriented systems like SPDBS have some limitations on the extension and integration of the heterogeneous databases. In this paper, we extend previous SPDBS into a web service prototype (SPDBSW) where all functions can be serviced on the web environment. The web services include pathway database integration/search, import/export of SBML documents, pathway reconstruction/visualization. SPDBSW has been implemented by the combination SPDBS and external web services such as OLS, KEGG and NCBI. And user can get more confidential and delicate information from KEGG or NCBI through their web services. The system can be extended or modified immediately by replacing its component web services. We provide SPDBSW at the website http://database.chungbuk.ac.kr/SPDBSW.

The 90 Day Challenge team set out to deliver an end-to-end Web services solution to enterprise sales agents in 90 days, with immediate plans to extend the solution to other user groups. In order to meet their commitments, the team had to reuse the same component Web services in multiple contexts. By modeling the workflows and carefully managing scope at the component level, the team developed a suite of Web services that other teams could easily incorporated into multiple projects. As a result, twelve other programs to date have incorporated Web services from the 90 Day Challenge, saving weeks of development time.

Tagging technique is widely used to annotate objects in Web 2.0 applications. Tags can support web service understanding, categorizing and discovering, which are important tasks in a service-oriented software system. However, most of existing web services' tags are annotated manually. Manual tagging is time-consuming. In this paper, we propose a novel approach to tag web services automatically. Our approach consists of two tagging strategies, tag enriching and tag extraction. In the first strategy, we cluster web services using WSDL documents, and then we enrich tags for a service with the tags of other services in the same cluster. Considering our approach may not generate enough tags by tag enriching, we also extract tags from WSDL documents and related descriptions in the second step. To validate the effectiveness of our approach, a series of experiments are carried out based on web-scale web services. The experimental results show that our tagging method is effective, ensuring the number and quality of generated tags. We also show how to use tagging results to improve the performance of a web service search engine, which can prove that our work in this paper is useful and meaningful.

Reputation is useful for establishing trust between Web service (WS) providers and WS consumers. In the context of WS composition, a challenging issue of reputation management is to propagate a user's impression of a composite WS (i.e., the user's feedback rating) to its component WSs. In this paper, we propose a Shapley value based approach which can achieve fair impression propagation, that is, the reputation of a component WS is never awarded (or penalized) for the good (or bad) performances of the other peer component WSs in the same composite WS. The fairness of the proposed approach is validated through theoretical analysis and experimental results.

Web services are the newest trend in information technology, being considered the most used alternative for building distributed open systems. Although currently Web services involve a single client-server access, the market is demanding cooperative Web services to provide a global solution. Recently software agents appear as a good option that can cope with the control of Web services composition, obtaining an integral solution. This paper presents an approach to integrate Web services and software agent technologies. The basis of our approach is the use of the component technology for the development of adaptive software agents. Our compositional software agent performs automated software composition based on the flexibility provided by the component orientation, which makes possible to plug Web services into the agent functionality and compose them during the agent interaction.KeywordsResource Description FrameworkSoftware AgentSimple Object Access ProtocolNegotiation ProtocolAgent FunctionalityThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

This paper describes a generalized web-based framework for VBI pathosystems informatics & bioinformatics web services. The framework provides a universal mechanism for accessing web services through web browsers. A web service can be configured to the framework easily. The framework is designed using object-oriented methodology and implemented using Java 2 Enterprise Edition, relational databases, XML technology and various other open source technologies. It is designed to conform to a n-tiered architecture that includes several layers: a web-based graphical user interface built using Apache Struts web framework running on Apache Jakarta Tomcat; a business object layer, server and web service components that process the queries and manipulate the result sets; and a robust data access layer. The system provides an extensible, flexible, and user-friendly framework for any generic bioinformatics projects, including genome curation, micro-array gene expression profiles, pathogen information curation and pathway analysis, etc.