We devise in this paper a Multilevel Adaptive Reduction Technique (MART) for time series data. MART extracts the main features of a time series and encodes them in a reduced data structure called reduct. The extracted features are leveraged to establish a distance between reducts that satisfies the lower bounding constraint. Furthermore, we show how MART can be further applied on the reduced data and operate at different levels. We conduct experiments on time series datasets that show MART based classification accuracy and multilevel reduction power. We present also a comparative study with well-known SAX based time series reduction techniques and deep learning time series classification techniques.

We propose in this paper a new HyperGraph-based Similarity Algorithm (HGSA) to measure the semantic similarity between services with focus on Web services. HGSA relies on a term-similarity function that considers several parameters such as node’s local density, depth, number of relation factors, and link strength. This function is leveraged to build a similarity matrix between Web services. Computing the similarity between Web services is reduced to applying the Hungarian method to this matrix. We study the complexity of the proposed algorithm and provide experiments that show that it outperforms other related approaches in terms of accuracy.

This paper looks into ways of supporting social Web services react to the behaviors that their peers expose at run time. Examples of behaviors include selfishness and unfairness. These reactions are associated with actions packaged into capabilities. A capability allows a social Web service to stop exchanging private details with a peer and/or to suspend collaborating with another peer, for example. The analysis of capability results into three types referred to as functional (what a social Web service does), non-functional (how a social Web service runs), and social (how a social Web service reacts to peers). To avoid cross-cutting concerns among these capabilities aspect-oriented programming is used for implementing a system.

By handling the orchestration, composition and interaction of Web services, the Business Process Execution Language (BPEL) has gained tremendous interest. However, such process-based language does not assure a secure environment for Web services composition. The key solution cannot be seen as a simple embed of security properties in the source code of the business logic since the dynamism of the BPEL process will be affected when the security measures get updated. In this context, several approaches have emerged to tackle such issue by offering the ability to specify the security properties independently from the business logic based on policy languages. Nevertheless, these languages are complex, verbose and require programming expertise. Owing to these difficulties, specifying and the enforcing BPEL security policies become very tedious tasks. To mitigate these challenges, we propose in this paper, a novel approach that takes advantage of both the Unified Modeling Language (UML) and the Aspect Oriented Paradigm (AOP). By elaborating a UML extension mechanism, called UML Profile, our approach provides the users with model-based capabilities to specify aspects that enforce the required security policies. On the other hand, it offers a high level of flexibility when enforcing security hardening solutions in the BPEL process by exploiting the AOP approach. We illustrate our approach through an example of the dynamic generation and integration of model-based security aspects in a BPEL process.

This paper investigates techniques for supporting individual users in choosing appropriate Web services according to their specific needs, and accessing their favorite Web services. It also examines the provision of visualization of Web services that can be made available to service consumers as well as service providers who promote their Web services. To achieve these goals, we propose a three-layer architecture: a data layer for handling measurements of quality attribute of Web services; a Web service middleware processing layer, which computes quality attribute weights for ranking Web services; and finally, a visualization layer for monitoring the quality of Web services. The proposed architecture is implemented and tested on real world Web services drawn from the QWS database of Web services. Our Web services visualization technique is more convenient and user-friendly compared to current basic text based Web services discovery techniques.

With the increasing popularity of using Web services, Quality of Service (QoS) is becoming a significant concern for both service consumers and providers. Several models for considering functional and non-functional QoS requirements for the purpose of Web service discovery and selection have been proposed. We present in this paper a new Web services selection model based on fuzzy logic. In this model, the non-functional QoS requirements are taken into account for the appropriate selection of required services. Our model can handle consumers' imprecise preferences with fuzzy sets. Moreover, a new fuzzy ranking algorithm that is based on the dependencies between quality attributes is proposed. The experimental results obtained from real world Web service domains revealed better performance of our algorithm compared to Entropy-based ranking algorithms.

We present in this paper a trust-based game theoretical model for Web services collaboration. The devised model is an application of the generic model about tasks allocation for agents, which is presented in. We consider that a collaboration between Web services captures a possible interaction for achieving a specific task. We consider such collaboration as a game in which several Web services compete to win a task by bidding a cost for achieving it. The game winner is the Web service which has the minimal trust-based cost, which is the product of the cost and the inverse of the trust value of the bidding Web service. Initial trust values are computed based on the distance between the actual and the announced quality attribute values of a Web service. These values are computed during a collaboration evaluation period. They are updated after each game round based on a bayesian model. We show in this paper how the use of trust allows a safer collaboration between Web services with respect to collaborations where there is no consideration of the trust as a criteria for allocating tasks.

We propose in this paper a new approach for the dynamic enforcement of Web services security, which is based on a synergy between Aspect-Oriented Programming (AOP) and composition of Web services. Security policies are specified as aspects. The elaborated aspects are then weaved (integrated) in the Business Process Execution Language (BPEL) process at runtime. The main contributions of our approach are threefold: (1) separating the business and security concerns of composite Web services, and hence developing them separately (2) allowing the modification of the Web service composition at run time and (3) providing modularity for modeling cross-cutting concerns between Web services. We demonstrate the feasibility of our approach by developing a Flight System (FS) that is composed of several Web services. First, a RBAC (Role Based Access Control) model for the flight system, which we called RBAC-FS, is elaborated. Afterwards, the Web services that implement the security features are developed. Finally, the BPEL aspects that integrate the security functionalities dynamically into the BPEL process are created. The devised aspects realize the elaborated RBAC-FS model and provide authentication and access control features to the flight system. Case studies and experimental results are also presented to defend our propositions.

Examining interactions between Web services is of paramount importance to the success of service composition. We have previously proposed a 2-layer framework for modeling, analyzing, and managing these interactions. Interactions are assigned to two layers: business logic and support. The business-logic layer comprises control and transactional flows, whereas the support layer comprises exception and message flows. This paper continues this research effort by focusing on the synchronization of the four flows at run-time. In particular, we discuss the synchronization mechanisms integrated into the 2-layer framework and report our preliminary experiments on the implementation.

Web service composition is currently a very focused-on topic of research, with many studies being proposed by academic and industrial research groups. This paper discusses the design and verification of behavior of composite Web services. We model composite Web services based on two behaviors, namely control and operational. These behaviors communicate through conversation messages. We use state charts to model composite Web services and verify the synchronization of the conversations among them using symbolic model checking with NuSMV.

This paper discusses how interactions between Web services engaged in composition scenarios are analyzed, modeled, and finally managed. Interactions are primarily considered as a means for conveying messages of different natures between separate components, for instance, Web services. To achieve better coordination and hence, avoid conflicts between Web services, in this paper interactions are handled by two layers known as business logic and support. The business-logic layer is the host of two flows known as control and transactional, whereas the support layer is the host of two additional flows namely exception and message. On top of the proposed layers and flows, context and policies are used to oversee the progress of interactions between Web services and to constrain the behavior of these Web services, respectively.

This paper discusses the compatibility issue between policies of Web services, which could refrain the automatic composition of these Web services from smoothly progressing. Policies regulate/constrain the functioning of Web services at three levels identified by business, behavior, and privacy. Because independent Web services collaborate with one another in order to satisfy users' needs, their respective policies could be in contradiction. This could lead to conflicts and exceptions at run-time unless these contradictions are as a first step, detected and then, fixed. In this paper, WSPL is the language to specify policies of Web services.

This paper presents an agent-based and context-oriented approach that supports the composition of Web services. A Web service is an accessible application that other applications and humans can discover and invoke to satisfy multiple needs. To reduce the complexity featuring the composition of Web services, two concepts are put forward, namely, software agent and context. A software agent is an autonomous entity that acts on behalf of users and the context is any relevant information that characterizes a situation. During the composition process, software agents engage in conversations with their peers to agree on the Web services that participate in this process. Conversations between agents take into account the execution context of the Web services. The security of the computing resources on which the Web services are executed constitutes another core component of the agent-based and context-oriented approach presented in this paper.

This work presents an approach for the dynamic management of the content of several Universal Description, Discovery, and Integration (UDDI) registries. By content, it is meant the announcements of Web services that providers post on various distributed UDDI registries. Unlike other initiatives in the field of Web services, our concerns are the following: availability of several UDDI registries, no predefined communication infrastructure between the UDDI registries, and no centralized component to coordinate the UDDI registries. The solution presented in this paper integrates users and software agents into what we call messengers. When a user is in the vicinity of an UDDI registry, his software agent, which resides in his mobile device, interacts with that registry. The objective is to submit the details on Web services that are stored in the mobile device.