Web Service Composition Research Articles

Achieving autonomic Web service compositions with models at runtime

Several exceptional situations may arise in the complex, heterogeneous, and changing contexts where Web service operations run. For instance, a Web service operation may have greatly increased its execution time or may have become unavailable. The contribution of this article is to provide a tool-supported framework to guide autonomic adjustments of context-aware service compositions using models at runtime. During execution, when problematic events arise in the context, models are used by an autonomic architecture to guide changes of the service composition. Under the closed-world assumption, the possible context events are fully known at design time. Nevertheless, it is difficult to foresee all the possible situations arising in uncertain contexts where service compositions run. Therefore, the proposed framework also covers the dynamic evolution of service compositions to deal with unexpected events in the open world. An evaluation demonstrates that our framework is efficient during dynamic adjustments.

An approach based on the transferrable belief model for trust evaluation in web services

Considering the existence of a wide range of web services and their diversity, selecting a service with the best performance among similar services remains a challenge for the demanding users. However, sometimes it is necessary that web services invoke each other and become combined to create a more complex composite web service. Evaluation of the trust degree based on the trust of individual services forming composite ones can be an effective factor for choosing the best combination of web services. In this paper, by using the fundamental concepts of belief combination and transferability in transferable belief model (TBM), the ratings of a customer for different interactions are combined to constitute the direct trust value. This creates a requirement to take the uncertainty of beliefs into account as well. In direct trust evaluation, the time of ratings determines the impact of the ratings in the final combination. By using the generalized Bayesian theorem in TBM, the trust of the composite services is modeled through time by considering the structure of the individual components within the service. Subsequently, it is shown that the proposed model provides a flexible mechanism for composite trust evaluation, it provides more accurate calculations compared to other existing models, and it is capable of taking into account more complex parameters in trust calculations such as the consistency of opinions.

Dynamic Composition of Web Services by Service Invocation Dynamically

Dynamic Composition of Web Services by Service Invocation Dynamically

Using Pi-calculus to Model Dynamic Web Services Composition Based on the Authority Model

ABSTRACTThere are numerous research articles on web service, composition, modeling, verification, and other problems. These research works are performed on the basis of formal methods, such as petri-net, pi-calculus, automata theory, and so on. Pi-calculus is a natural vehicle to model the mobility aspect in dynamic web services composition (DWSC). However, it has recently been shown that pi-calculus needs to be extended suitably to specify and verify DWSC. In this article, we consider the authority model for DWSC, extend pi-calculus in order to model dynamic attributes of system, and propose a automatic method for modeling DWSC based on extended pi-calculus.

Integrating Trust with User Preference for Effective Web Service Composition

Web service composition is a process to compose homogenous or heterogeneous services together in order to create value-added services. Many non-functional features including QoS and user preferences have been adopted to guide such a process. However, two issues are observed: (1) the expressiveness of user preference is subject to quantitative preferences without proper use of qualitative preferences; (2) a highly preferred composite service may not be trustworthy, or a highly trustworthy composite service may not be preferable. The existing studies concentrate on either user preference or service trust, and fail to provide a systematic solution to integrate both user preference and service trust together for service compositions. To address these issues, we combine both qualitative and quantitative preferences as well as service trust together in the process of service composition. We investigate the application of heuristic algorithms on multi-objective optimization for the service composition problem. A new hybrid nature inspired intelligent algorithm is also proposed and compared with other popular heuristic algorithms. We aim to obtain optimal web service compositions that can satisfy these (potentially conflicting) constraints as much as possible. Results demonstrate the efficiency and effectiveness of our approach in comparison with other counterparts.

A quality-controlled logic-based clustering approach for web service composition and verification

PurposeService-oriented architecture is an emerging software architecture, in which web service (WS) plays a crucial role. In this architecture, the task of WS composition and verification is required when handling complex requirement of services from users. When the number of WS becomes very huge in practice, the complexity of the composition and verification is also correspondingly high. In this paper, the authors aim to propose a logic-based clustering approach to solve this problem by separating the original repository of WS into clusters. Moreover, they also propose a so-called quality-controlled clustering approach to ensure the quality of generated clusters in a reasonable execution time.Design/methodology/approachThe approach represents WSs as logical formulas on which the authors conduct the clustering task. They also combine two most popular clustering approaches of hierarchical agglomerative clustering (HAC) and k-means to ensure the quality of generated clusters.FindingsThis logic-based clustering approach really helps to increase the performance of the WS composition and verification significantly. Furthermore, the logic-based approach helps us to maintain the soundness and completeness of the composition solution. Eventually, the quality-controlled strategy can ensure the quality of generated clusters in low complexity time.Research limitations/implicationsThe work discussed in this paper is just implemented as a research tool known as WSCOVER. More work is needed to make it a practical and usable system for real life applications.Originality/valueIn this paper, the authors propose a logic-based paradigm to represent and cluster WSs. Moreover, they also propose an approach of quality-controlled clustering which combines and takes advantages of two most popular clustering approaches of HAC and k-means.

Event tree algorithms to generate test sequences for composite Web services

SummaryIn service‐oriented architecture testing, the behaviour of a composite service and its partner services can be represented as an event graph (model). As test cases are derived from such a model, the Chinese postman problem (CPP) algorithm is applied to cover all edges. Although CPP provides an optimal solution, there is a lack of alternative algorithms to obtain not only a faster execution but also a satisfactory solution. This paper introduces the event tree algorithm (ETA) to generate test cases from event sequence models for Web service compositions. Two strategies are also proposed to improve ETA: First, a greedy strategy to build the tree is defined based on the cost of expanding given edges. Second, redundant elements are eliminated (pruned) in the tree. Four versions of ETA are compared with CPP with respect to test suite size, generation time, number of test sequences, and test sequence length.

A Distributed Infrastructure to Support Scientific Experiments

[Context] Significant changes are occurring in the scientific scenario. In particular, there is increasing collaboration among researchers, which has led to the increasing use of processing techniques and the need to share results and observations. Researchers usually need to compose experiments using available services to fulfill their requirements. However, finding and/or specifying scientific applications is not a trivial task and many scientists lack the computational knowledge necessary to compose their experiments. [Objective] Therefore, the objective of this work is to develop an infrastructure in which researchers can work with heterogeneous information, accessing scientific communities according to their interests. As a result, they can create new experiments with the help of compositions of semantic web services. [Methods] Considering the infrastructure model, a prototype was specified and evaluated in a real-world context. [Results] This evaluation found evidence for the feasibility of the use of this infrastructure in scientific scenarios. Therefore, this paper proposes a distributed platform where scientists can collaborate in order to specify an experiment and share its results, considering semantic information. This is in agreement with the ideas of “collaboratories”.

A distributed authentication model for composite Web services

Proliferation of Web services based applications, collaboration and interoperability between companies, extremely heterogeneous policies of security, and, more generally, reply attacks over Internet are major challenges in the design of security infrastructures for Web services. In this paper, we focus our study on authentication of composite Web services. Authentication is certainly at the heart of any secure system. Thus, we propose a distributed model of authentication based on the circle of trust concept for composite Web services. This model has several functionalities: First, it ensures authentication for arbitrary composite Web services over Internet. Second, it can process across and beyond domain authentication boundaries. Third, it takes over the conflicts of security policies using the concept of Web Single Sign On (SSO) and client's profile using ontologies. Furthermore, the proposed model is scalable and dynamic because it is designed in a fully distributed manner, there are no central points and it evolves over time. An implementation of a prototype and a simulation design demonstrate that a strong security can be achieved for both the client and the composite Web service through the combination of a dynamic and collaborative trust model with a number of enhancements: (i) a combined encryption technique, (ii) a distributed authority of certificates, and (iii) semantic annotations.

CASAS: A tool for composing automatically and semantically astrophysical services

Multiple astronomical datasets are available through internet and the astrophysical Distributed Computing Infrastructure (DCI) called Virtual Observatory (VO). Some scientific workflow technologies exist for retrieving and combining data from those sources. However selection of relevant services, automation of the workflows composition and the lack of user-friendly platforms remain a concern. This paper presents CASAS, a tool for semantic web services composition in astrophysics. This tool proposes automatic composition of astrophysical web services and brings a semantics-based, automatic composition of workflows. It widens the services choice and eases the use of heterogeneous services. Semantic web services composition relies on ontologies for elaborating the services composition; this work is based on Astrophysical Services ONtology (ASON). ASON had its structure mostly inherited from the VO services capacities. Nevertheless, our approach is not limited to the VO and brings VO plus non-VO services together without the need for premade recipes. CASAS is available for use through a simple web interface.

Domain-aware Mashup service clustering based on LDA topic model from multiple data sources

ContextMashup is emerging as a promising software development method for allowing software developers to compose existing Web APIs to create new or value-added composite Web services. However, the rapid growth in the number of available Mashup services makes it difficult for software developers to select a suitable Mashup service to satisfy their requirements. Even though clustering based Mashup discovery technique shows a promise of improving the quality of Mashup service discovery, Mashup service clustering with high accuracy and good efficiency is still a challenge problem. ObjectiveThis paper proposes a novel domain-aware Mashup service clustering method with high accuracy and good efficiency by exploiting LDA topic model built from multiple data sources, to improve the quality of Mashup service discovery. MethodThe proposed method firstly designs a domain-aware Mashup service feature selection and reduction process by refining characterization of their domains to consolidate domain relevance. Then, it presents an extended LDA topic model built from multiple data sources (include Mashup description text, Web APIs and tags) to infer topic probability distribution of Mashup services, which serves as a basis of Mashup service similarity computation. Finally, K-means and Agnes algorithm are used to perform Mashup service clustering in terms of their similarities. ResultsCompared with other existing Mashup service clustering methods, experimental results show that the proposed method achieves a significant improvement in terms of precision, recall, F-measure, purity and entropy. ConclusionThe results of the proposed method help software developers to improve the quality of Mashup service discovery and Mashup-based software development. In the future, there will be a need to extend the method by considering heterogeneous network information among Mashup, Web APIs, tags, users, and applying it to Mashup discovery for software developers.

Computational Intelligence Based QoS-Aware Web Service Composition: A Systematic Literature Review

Web service composition concerns the building of new value added services by integrating the sets of existing web services. Due to the seamless proliferation of web services, it becomes difficult to find a suitable web service that satisfies the requirements of users during web service composition. This paper systematically reviews existing research on QoS-aware web service composition using computational intelligence techniques (published between 2005 and 2015). This paper develops a classification of research approaches on computational intelligence based QoS-aware web service composition and describes future research directions in this area. In particular, the results of this study confirms that new meta-heuristic algorithms have not yet been applied for solving QoS-aware web services composition.

Semi-Markov Models of Composite Web Services for their Performance, Reliability and Bottlenecks

When combining several services into a composite service, it is non-trivial to determine, prior to service deployment, performance and reliability values of the composite service. Moreover, once the service is deployed, it is often the case that during operation it fails to meet its service-level agreement (SLA) and one needs to detect what has gone wrong (i.e., performance/reliability bottlenecks). To study these issues, we develop a Semi-Markov Process (SMP) formulation of composite services with failures and restarts. By explicitly including failure states into the SMP representation of a service, we can compute both its performance and reliability using a single SMP. We can also detect its performance and reliability bottlenecks by applying the formal sensitivity analysis technique. We demonstrate our approach by choosing a representative example that is validated using experiments on real web services.

Web Service Composition: A Survey on the Various Methods used for Web Service Composition

This paper is a survey about the constantly evolving web services, their composition methods and the various problems and challenges that they faced. The paper aims to provide an overview of numerous Web Service technologies like WSDL, UDDI, SOAP etc. The paper also provides insights about composition/processes like WS-CDL (Web Services Choreography Description Language), BPEL etc. The intention of this survey is to help the reader to understand about the different problems that were faced by the different composition methods while also providing information regarding the various aspects of Web Services. Keywords: Web Services, SOA, WSDL, BPEL4WS, Web Service Composition, Orchestration, RESTful services, Composition Methods.

A clustering network-based approach to service composition in cloud manufacturing

Cloud manufacturing (CMfg) is a new business paradigm that aims to provide manufacturing resources as services over the Internet in a convenient pay-as-you-go mode. Service composition is a critical means for achieving value adding and synergy of resources in CMfg. There are a vast number of services in a CMfg platform, which makes traditional service composition methods incapable and low efficiency in solving the problem of service composition. Most of existing research on CMfg was devoted to the optimal selection of services under a specific composition flow and a group of given candidate pools. Hence, there is a need to explore effective approaches to obtaining service composition flow and candidate sets. The network-based web service composition approach has recently drawn much attention and has been proved effective in coping with the challenge of large-scale services. Inspired by this, a novel approach called service clustering network-based service composition is proposed in this paper. In this method, services are first clustered into abstract services, and then a clustering network of the abstract services is established. In this way, service composition paths and corresponding candidate sets for fulfilling manufacturing tasks can be quickly obtained without requiring task decomposition, which decreases the difficulty and improves efficiency of service composition. Effectiveness and efficiency of the approach are verified through simulation experiments.

Dynamic Construction Scheme for Virtualization Security Service in Software-Defined Networks.

For a Software Defined Network (SDN), security is an important factor affecting its large-scale deployment. The existing security solutions for SDN mainly focus on the controller itself, which has to handle all the security protection tasks by using the programmability of the network. This will undoubtedly involve a heavy burden for the controller. More devastatingly, once the controller itself is attacked, the entire network will be paralyzed. Motivated by this, this paper proposes a novel security protection architecture for SDN. We design a security service orchestration center in the control plane of SDN, and this center physically decouples from the SDN controller and constructs SDN security services. We adopt virtualization technology to construct a security meta-function library, and propose a dynamic security service composition construction algorithm based on web service composition technology. The rule-combining method is used to combine security meta-functions to construct security services which meet the requirements of users. Moreover, the RETE algorithm is introduced to improve the efficiency of the rule-combining method. We evaluate our solutions in a realistic scenario based on OpenStack. Substantial experimental results demonstrate the effectiveness of our solutions that contribute to achieve the effective security protection with a small burden of the SDN controller.

Evolutionary computation for automatic Web service composition: an indirect representation approach

Web services have become increasingly popular in recent years, and they are especially suitable to the process of Web service composition, which is when several services are combined to create an application that accomplishes a more complex task. In recent years, significant research efforts have been made on developing approaches for performing Quality of Service -aware Web service composition. Evolutionary computing (EC) techniques have been widely used for solving this problem, since they allow for the quality of compositions to be optimised, meanwhile also ensuring that the solutions produced have the required functionality. Existing EC-based composition approaches perform constrained optimisation to produce solutions that meet those requirements, however these constraints may hinder the effectiveness of the search. To address this issue, a novel framework based on an indirect representation is proposed in this work. The core idea is to first generate candidate service compositions encoded as sequences of services. Then, a decoding scheme is developed to transform any sequence of services into a corresponding feasible service composition. Given a service sequence, the decoding scheme builds the workflow from scratch by iteratively adding the services to proper positions of the workflow in the order of the sequence. This is beneficial because it allows the optimisation to be carried out in an unconstrained way, later enforcing functionality constraints during the decoding process. A number of encoding methods and corresponding search operators, including the PSO, GA, and GP-based methods, are proposed and tested, with results showing that the quality of the solutions produced by the proposed indirect approach is higher than that of a baseline direct representation-based approach for twelve out of the thirteen datasets considered. In particular, the method using the variable-length sequence representation has the most efficient execution time, while the fixed-length sequence produces the highest quality solutions.

Development and Composition of E-Learning Web Services Using Service Oriented Architecture

In recent era of cloud computing, web service technology has become the most important and popular technology to generate and provide dynamic web services. The utility computing and on-demand services are the basic characteristics of cloud computing, where any legacy web application can be converted into dynamic web services as per the requirements. Some web services need to be combined with defined business logic or rules to satisfy the customer. Web service composition is the cost-effective way of developing combined services for any web application. Web services are services with standard interfaces that provide specific functionality of application. Web services are usually implemented using Service Oriented Architecture (SOA). Web services are combined to make two or more web services communicate with each other to provide combined functionality. To make service oriented architecture effective, services needs to be identified and defined correctly. In this paper, a methodology is defined to identify, implement and combine the web services for an e-learning application. An E-learning application is created by using various web services and combined by specifying certain rules. E-learning is an electronic educational technology where the e-learning portal is implemented using SOA approach. The paper aims at three main objectives: web services creation, composition of web services and handling the exceptions for composition. The four main web services considered for e-learning application are contents, quiz, assignment and forum. Web services are combined using Orchestration and Choreography techniques and compared with the response time of the services execution

A Proposal for a Comparison Framework for the Management of Variability in Web Services Composition

A Proposal for a Comparison Framework for the Management of Variability in Web Services Composition

A Proposal for a Comparison Framework for the Management of Variability in Web Services Composition

A Proposal for a Comparison Framework for the Management of Variability in Web Services Composition