Web services are becoming the prominent paradigm for distributed computing and electronic business. This has raised the opportunity for service providers and application developers to develop value-added services by combining existing web services. However, current web service composition solutions do not address software engineering principles for raising the level of abstraction in web-services by providing facilities for packaging, re-using, specializing and customizing service compositions.In this paper we propose the concept of service component that packages together complex services and presents their interfaces and operations in a consistent and uniform manner in the form of an abstract class definition, Service components are internally synthesized out of reused, specialized, or extended complex web services and just like normal web services are published and can thus be invoked by any service-based application. In addition, we present an integrated framework and prototype system that manage the entire life-cycle of service components ranging from abstract service component definition, scheduling, and construction to execution.

Service components for managing the life-cycle of service compositions

Hybrid composite materials are the result of a combination of several phases where at least two reinforcement elements are integrated into a matrix to improve the composite's properties. The morphology, nature, and orientation of components are significantly affect the manner that composite react against solicitations. In fact, the properties of the composite are closely linked to its internal structures, which are governed by the characteristic properties of the constituent elements of the composite. The heterogeneity problem of composite materials at the microscopic level makes it difficult to move toward a homogeneous global level where the behavior of the material can be measured. In this chapter, the classifications of composite materials and filler types are presented. Then, the renowned analytical models, including the Voigt and Reuss method, Hirsh's method, Tsai's model, other analytical models, are discussed. Next, a review of proposed models for the properties of the hybrid composite material in two cases is debated, beginning with numerical modeling of fiber hybridization using the linear rule-of-mixture of Zweben and Fukuda, and finishing with numerical modeling of hybrid particulate fiber-reinforced composites using three approaches: representative volume element, representative unit cell, and object-oriented modeling.

Numerical modeling of hybrid composite materials

Business process outsourcing to the cloud: Balancing costs with security risks

Companies are ready to outsource their business process to the cloud to enjoy its benefits. However they must be sure that their business know-how is preserved. Although some solutions already exist and consist in splitting the model into a collaboration of BP fragments for a deployment in a muti-cloud context, none of them takes into account the possibility of collusion between the clouds executing the different fragments. To address this issue, we propose in this paper a solution consisting in adding fake BP fragments at specific locations in the process, so as to complicate its structure and hide the direct interaction between clouds executing sensitive fragments. Therefore, the discovery of the process by malicious cloud providers is delayed. The approach is validated against an introduced metric. It demonstrates that our approach is better in the worst case than previous approaches in best cases.

/pdf/obfuscating-a-business-process-by-splitting-its-logic-with-3sqgl68irg.pdf

Obfuscating a Business Process by Splitting Its Logic with Fake Fragments for Securing a Multi-cloud Deployment

Formal techniques for consistency checking of orchestrations of semantic Web services

Bounding models families for performance evaluation in composite Web services

Business process (BP) stakeholders want to enjoy the benefits of the cloud, but they are also reluctant to expose their BP models which express the know-how of their companies. To prevent such a know-how exposure, this paper proposes a design-time approach for transforming a BP model into BP fragments so that these BP fragments externalized in a multi-cloud context do not allow a cloud resource provider to understand a critical fragment of the company. While existing contributions on this topic remain at the level of principles, we propose an algorithm supporting automatically such a BP model transformation.

/pdf/paving-the-way-towards-semi-automatic-design-time-business-31uiax7vbh.pdf

Paving the Way towards Semi-automatic Design-Time Business Process Model Obfuscation

A workflow process defines a set of activities and the specific order according to which they should be executed in order to achieve a common objective. The correctness and efficiency of the business process supported by the workflow management are vital, in particular the k-soundness property when processes are modeled by workflow nets (WF-nets). This property entails the proper termination of the workflow execution and the absence of tasks that do not contribute to the processing cases. Furthermore, business processes are not isolated and in order to support the global performance of a given organization, they should well articulated, and correctly synchronized to each other. Nevertheless, without specific conditions, the k-soundness criterion is not compositional while it should remain valid for the set articulated processes. We propose in this paper a set of compositional rules that allow to build complex workflows from single ones while preserving k-soundness property under elementary conditions. Moreover, for the free-choice Petri net class we show that the soundness property verification can be efficiently checked.

Business Process Compositions Preserving k-Soundness Property

Multi-tenancy enables cost-effective SaaS through resource consolidation. Multiple customers, or tenants, are served by a single application instance, and isolation is enforced at the application level. Service load for different tenants can vary over time, requiring applications to scale in and out. A large class of SaaS providers operates legacy applications structured around a relational (SQL) database. These applications achieve tenant isolation through dedicated fields in their relational schema and are not designed to support scaling operations. We present a novel solution for scaling in or out such applications through the migration of a tenant’s data to new application and database instances. Our solution requires no change to the application and incurs no service downtime for non-migrated tenants. It leverages external tables and foreign data wrappers, as supported by major relational databases. We evaluate the approach using two multi-tenant applications: Iomad, an extension of the Moodle Learning Management System, and Camunda, a business process management platform. Our results show the usability of the method, minimally impacting performance for other tenants during migration and leading to increased service capacity after migration.

/pdf/a-methodology-for-tenant-migration-in-legacy-shared-table-20nlycw0ds.pdf

A Methodology for Tenant Migration in Legacy Shared-Table Multi-tenant Applications

With the generalization of the Cloud, software providers can distribute their software as a service without investing in large infrastructure. However, without an effective resource allocation method, their operation cost can grow quickly, hindering the profitability of the service. This is the case for BPM as a Service providers that want to handle hundreds of customers with a given quality of service. Since there are variations in the capacity and the number of users, the allocation method must be able to adjust the resource and the allocation of customer on these resources. In this paper we present a cost optimization model and a heuristic based on genetic algorithms to adjust resource allocation to the need of a set of customers with varying BPM task throughput. Experi-mentations using realistic customer loads and cloud resources capacities shows the gain of this method compared to previous approaches.

https://hal.archives-ouvertes.fr/hal-01558202/document

Samir Youcef

Papers

Bounding models families for performance evaluation in composite Web services

Paving the Way towards Semi-automatic Design-Time Business Process Model Obfuscation

Business Process Compositions Preserving k-Soundness Property

A Methodology for Tenant Migration in Legacy Shared-Table Multi-tenant Applications

Optimisation of business process tenant distribution in the Cloud with a genetic algorithm