Flexible and adaptive quality-of-service (QoS) is desirable for distributed real-time applications, such as e-commerce, or multimedia applications. The objective of this research is to dynamically instantiate composite services by effectively utilising the collective capabilities of the resources to deliver distributed applications. Related to this objective are the problems of: (1) predicting system and network resources utilisation as well as the user's changing requirements on the provided services, and (2) finding optimal execution plans for a service that meet end-to-end quality requirements and adapting the available resources in accordance to the changing situation. This paper presents a framework for adaptive QoS and resource management in provisioning composite services. We also develop distributed algorithms for finding the multi-constrained optimal execution plan to enable delivery of QoS-assured composite services.