The Internet of Things (IoT), smart sensors and mobile wearable devices are helping to provide services that are more ubiquitous, smarter, faster and easily accessible to users. However, security is a significant concern for the IoT, with access control and identity management are being two major issues. With the growing size and presence of these systems and the resource constrained nature of the IoT devices, an important question is how to manage policies in a manner that is both scalable and flexible. In this research, we aim at proposing a fine-grained and flexible access control architecture, and to examine an identity model for constrained IoT resources. To achieve this, first, we outline some key limitations in the state of the art access control and identity management for IoT. Then we devise our approach to address those limitations in a systematic way.