Methods and apparatus, including computer program products, for real-time and context-aware tracking of items. Tags bound to items are read and information read from the tags and location information about the tags is provided by at least two enterprises and used to maintain disposition information about the items, which is made visible to enterprises in the supply chain. The disposition information can be mapped to a world model that tracks the items and circumstances affecting the items, for example, geo-spatial events and traffic delays. Visibility of the disposition information can be controlled through authorization. Visible information can include relationships between particular items and business documents such as order and shipping documents.