This document describes:
• key features of the socialized IoT systems, e.g. sensing the external physical world, resolving the uncertainties of targets, satisfying users' demand and providing quality service, etc.;
• socialized attributes, i.e. socialized network, socialized collaboration, and socialized services, which are derived from the key features; and
• guidelines on how to use or apply the socialized attributes in the design and development of IoT systems.