Web service interfaces

Web service interfaces are considered as one of the critical components of a Service-Oriented Architecture (SOA) and they represent contracts between web service providers and clients (subscribers). These interfaces are frequently modified to meet new requirements. However, these changes in a web service interface typically affect the systems of its subscribers. Thus, it is important for subscribers to estimate the risk of using a specific service and to compare its evolution to other services offering the same features in order to reduce the effort of adapting their applications in the next releases. In addition, the prediction of interface changes may help web service providers to better manage available resources (e.g. programmers’ availability, hard deadlines, etc.) and efficiently schedule required maintenance activities to improve the quality. In this paper, we propose to use machine learning, based on Artificial Neuronal Networks, for the prediction of the evolution of Web services interface design. To this end, we collected training data from quality metrics of previous releases from 6 Web services. The validation of our prediction techniques shows that the predicted metrics value, such as number of operations, on the different releases of the 6 Web services were similar to the expected ones with a very low deviation rate. In addition, most of the quality issues of the studied Web service interfaces were accurately predicted, for the next releases, with an average precision and recall higher than 82 %. The survey conducted with active developers also shows the relevance of prediction technique for both service providers and subscribers.

SOA and Web Services allow to easily expose business functions to build larger distributed systems. However, legacy systems – mostly in COBOL – are left aside unless applying a migration approach. Main approaches are: direct and indirect migration. The former implies to wrap COBOL programs with a thin layer of a Web Service oriented language/platform. The latter needs reengineering COBOL functions to a modern language/platform. In a previous work, we presented an intermediate approach based on direct migration where developed Web Services are later refactored to improve their interfaces quality. Refactorings mainly capture good practices inherent to indirect migration. In this paper, we measure the complexity of Web Services’ interfaces generated by the three approaches. Both comprehension and interoperability can be affected according to the service interface complexity level. We apply a metric suite (by Baski & Misra) to measure complexity on services interfaces – i.e., WSDL documents. Migrations of two real COBOL systems upon the three approaches were compared on the complexity level of the generated WSDL documents.

With the rapid development of Internet, Web Service technology is gradually applied to many areas of life. The security problems occurred in practical applications of Web Service has received more and more attention from the public. Aiming at the security problems existing in the application process of Web Service, a secure real-time internal and external network data exchange method based on Web Service protocol is proposed in this paper, it is agreed that the external network only allows data exchange with the internal network through the Web Service interface, that is, the internal network starts the Web Service service, the external network accesses the service, and then obtains the internal network data or informs the internal network for business processing. Web attack detection is put to the front end to ensure maximum security of Web Service system, which can meet the requirements of more secure and robust web applications while guaranteeing the business security of visitors.

It is common that multiple Web services coordinate to achieve a common goal. If two Web services happen to reside on the same runtime system, it is inefficient to communicate via Web services interface. This research proposes our short circuit switch (SCS), which is an intelligent Web services discovery and invocation engine that can be attached to deployed Web services. Our preliminary empirical experience shows that our short circuit switch engine exhibits high performance.

A web service interface contains information about the names of the operations that can be invoked on the service and the input and output parameters of these operations. This information is not enough to facilitate service developer and consumer in understanding the behavior of the service. In the context of RESTful web services, the requirements of RESTful interface should also be met that are not fulfilled by just advertising the allowed operations on the resources. In addition, RESTful services take hypermedia as an engine of application states. Such services are defined to be at level 3 of Richardson Maturity Model(RMM). In this paper, we present an approach to model the structural and behavioral interface of a RESTful web service using UML class and UML protocol diagrams. These models lead to RESTful interfaces that conform to level 3 of RMM and describe the behavior of operations in terms of preconditions and post-conditions. These models facilitate the authentication mechanism and provide clear mapping to HTTP requests and responses. The generated contracts of methods can be published in an extended version of the WADL language and also used for documentation, stub generation, testing and monitoring purposes.

MPI-based parallel applications including scientific applications are now widely executed on clusters and grids, and great benefits have been brought to scientific community. However, writing parallel applications would not be easy even for experienced programmers. In this paper, we propose the design and implementation of the MPI-SV middleware that connects gSOAP, the web service interface, and MPICH, the parallel software tool running on a Rocks cluster. With MPI-SV, users can automatically call parallel functions executed on a cluster as if they were regular functions. Hence, users do not have to write MPI-based parallel functions themselves.MPI-SV middleware is implemented on a Rocks cluster and complies with the SOAP standard specification so that it could interoperable with other web services. Three experiments based on numerical calculations are conducted, and the results show that the response time is increased when the data size increases. Even though sending data in MPI-SV via XML in SOAP incurs high communication overhead, our experimental results show that, for a parallel application requiring high computation, the overhead time would be low when compared with computation time. Thus, MPI-SV would give good performance for applications that the computation time dominates the communication time, and fortunately most scientific applications have high computation.

Most of the work on automated web service composition has focused so far on composition of stateful web services. This level of composition so-called "Process Level" considers web services with their internal and complex behaviors. At process level formal models such as State Transition Systems (STS from now) or Interface Automata are the most appropriate models to represent the internal behavior of stateful web services. However such models focus only on semantics of their behaviors and unfortunately not on semantics of actions and their parameters. In this paper, we suggest to extend the STS model, by following the WSMO based annotation for Abstract State Machine. This semantic enhancement of STS so called S2 TS will enable to model semantics of internal behaviors and semantics of their actions together with their input and output parameters. Secondly, we will focus on automated generation of data flow (or the process to perform automated assignments between parameter of services involved in a composition). Thus we do not restrict to assignments of exact parameters (which is practically never used in industrial scenario) but extend assignments to semantically close parameters (e.g., through a subsumption matching) in the same ontology. Our system is implemented and interacting with web services dedicated to Telecommunication scenarios. The preliminary evaluation results showed high efficiency and effectiveness of the proposed approach.

In this paper we evaluate the use of case-based classification to resolve a number of questions related to information sharing in the context of an Integrated Web services Brokering System (IWB). We are developing the IWB to independently decompose and analyze ad hoc Web services interface descriptions in order to identify Web services of interest. Our approach is to have the IWB cache information about each service in order to support an autonomous mediation process. In this mediation process, the IWB independently matches the user's data request to the correct method within the appropriate Web service, translates the user's request to the correct syntax and structure of the Web service request, dynamically invokes the method on the service, and translates the Web service response. We use casebased classification as a means of automating the IWB's analysis of relevant services and operations. Case-based classification retrieves and reuses decisions based on training data. We use sample Web Service Description Language (WSDL) files and schema from actual Web services as training data in our approach and do not require the service to pre-deploy an OWL-S ontology. We present our evaluation of this approach and performance ratings in the context of meteorological and oceanographic (MetOc) Web services as it relates to the IWB.

End-users conduct various on-line activities. Quite often they re-visit websites and use services to perform repeated activities, such as on-line shopping. The end-users are required to enter the same information into various web services to accomplish such repeated tasks. Typing redundant information repetitively into such services negatively impacts the user experience. In this study, we propose an approach to prevent end-users from such unnecessary interruption. Our approach propagates user inputs across services by linking similar input and output parameters. Our approach also pre-fills values to the input parameters which could not be filled by the values from other input or output parameters. We propose a meta-data model for storing user inputs and an Input Parameter Context Model for identifying similar input or output parameters. We have implemented our approach and evaluated it on the real world services through an empirical study. Our overall approach can reduce on average 37% of input parameters through the execution of composed services.

Web service architectures have gained popularity in recent years within the scientific grid research community. One reason for this is that web services allow software and services from various organizations to be combined easily to provide integrated and distributed applications. However, most applications developed and used by scientific communities are not web-service-oriented, and there is a growing need to integrate them into grid applications based on service-oriented architectures. In this paper, we describe a framework that allows scientists to provide a web service interface to their existing applications as web services without having to write extra code or modify their applications in any way. In addition, application providers do not need to be experts in web services standards, such as Web Services Description Language, Web Services Addressing, Web Services Security, or secure authorization, because the framework automatically generates these details. The framework also enables users to discover these application services, interact with them, and compose scientific workflows from the convenience of a grid portal.

This paper describes the architecture of an airport operation database system (AODBS), which is the most important part of airport information integration system (AIIS) developed by the author. This airport operation database system is a distributed computing system with a multi-layer structure and connected to the rest of the AIIS through web service and message queue interface. The application modules of AODBS are written in C#, web modules written in Java and client modules written in Delphi, the modules communicate with others through web service. In the system, an object-oriented (OO) model of airport operation is developed and object relational mapping (ORM) technique is used to connect the OO model and database. The airport operation database system consists of a database server, three application servers, a web server and about 100 clients. The Architecture of AODBS described in this paper is proved to be reasonable and efficient by actual operation in the airport.

Web services composition is a process of creating a new web service from a set of available web services. Semi-dynamic web services composition in Service Oriented Architecture (SOA) consists of designing composition plan by service provider, and automation of web service discovery and selection at runtime. This research paper describes redundant-free web services composition in order to reduce execution time and overall cost of the composition process and also improve efficiency of the composition method. To fulfill the needs, this paper uses a linked list data structure called Composition List (CL) to select the ideal services. In addition, a hash table called Available Output Parameters (AOP) is used to find redundant web services and reject them from web services composition process.

Spatio-temporal modelling of individual exposure to air pollution and its uncertainty

This paper proposes rethinking how ontologies are used to compose web services into business processes. Unlike handcrafted ontologies, we describe using a multi-agent system (MAS) to automatically generate semantic mappings from service interfaces. Comparing synonyms and contextual clues, we infer meanings of input and output parameters with no explicit semantics (as in a Web Services Description Language document). We further describe how this semantic mapping can be used to derive executable processes by comparing the derived ontologies of each service interface and mapping each service's outputs to inputs of every other service and finding the paths through the resulting graph.

Web services provide a standard means of interoperating between different software applications, running on a variety of platforms and/or frameworks. While the concepts of Web services are aimed at providing a standard means to support interoperable machine-to-machine interaction over a network, they do not solve the problem of between service requesters and providers. A trusted component is defined as a reusable software element possessing specified and guaranteed property qualities. The highly reusable nature of a Web service emphasizes the need for a trust ensuring mechanism between the requester and the provider of the service. The focus of this paper is to suggest a fortified Web services architecture introducing the concept of contracts to increase the level of between the requester and the provider of the requested service. In order to achieve this goal a new language is introduced into the fortified Web services architecture: WS-Contract. WS-Contract is a machine-processable specification of the Web service semantics, formally supporting the different levels of contract information. It defines the pre-and post conditions of the Web services interface, the synchronization policy of the service and the QoS parameters that should be maintained between the requester agent and the provider agent. WS-Contract relies, wherever possible, on existing Web services standards to build the necessary trust ensuring mechanism for Web services