Internet of Things (IoT) is considered as a future paradigm whose main challenge is to give an IP based transparent access to the huge number of services available as IoT resources. Due to the large number of resource-constrained devices and the dynamic nature of IoT environments, this integration problem becomes more intricate. The current state-of-the-art is mostly focused on the integration of IP enabled smart objects on the basis of Service Oriented Architecture (SOA) and the Representational State Transfer (REST) architectural style. However, beyond these approaches, we intend to address the flexible and adaptive composition of services in Very Large Scale (VLS) IoT systems by exploiting the concepts of service orchestration and choreography. In particular, we present an architectural model that enables efficient integration of services by locally orchestrating distributed web-enabled services in VLS IoT systems and globally choreographing Web-based applications.