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Service-oriented architecture (SOA) has become an application development paradigm widely recognized both in academia and in industry. Although SOA-based applications may vertically implement business processes through the composition of loosely coupled services, they have to face frequent changes, such as unavailability of service (due to the uncontrollable, dynamic, and distributed environments) or dynamic replacement of service (due to specific user requirements). This indicates that the service compositions are expected to be adaptable enough to cater to such changing situations. In this paper, we propose an approach to supporting unplanned dynamic changes of service compositions by combining variability management and dynamic binding. The proposed approach introduces the concept of abstract proxy services in a variability-supporting service composition language, namely VxBPEL, and provides a mechanism to support variation design and dynamic binding for unplanned changes at run time. To realize the proposed approach, we have developed a service composition engine that supports abstract proxy services and their run-time replacement via service discovery or user intervention. Finally, a case study has been conducted to demonstrate the feasibility of the proposed approach and quantify the performance overhead resulting from runtime variability management and dynamic binding. The experimental results show that the proposed approach overcomes the limitation of imperative variability-based approaches in handling unplanned dynamic changes and further enhances the dynamic adaptability of VxBPEL-based service compositions.

The publish/subscribe paradigm provides a loosely-coupled and scalable communication model for the large-scale IoT service systems, such as supervisory control and data acquisition (SCADA). Data confidentiality and service privacy are two crucial security issues for the publish/subscribe model deployed in different domains. The existing access control schemes for such model cannot address both the issues at the same time. In this paper, we propose a comprehensive access control framework (CACF) to bridge this gap. The design principle of the proposed framework is twofold: (a) a bi-directional policy matching scheme for protecting the privacy of IoT services; and (b) a fully homomorphic encryption scheme for encrypting published events to protect data confidentiality. We analyze the correctness and security of the CACF, moreover, we prototype CACF based on Apache ActiveMQ, an open source message broker, and evaluate its performance. The experimental results indicate that our security system meets the latency requirements for very high-quality SCADA services.