Methods and apparatus, including computer program products, for updating information on a writable tag bound to an article. In one aspect, a method includes: receiving in a system first attribute information for a first article derived from data read automatically from a first tag bound to the article; similarly receiving second attribute information for a second article; receiving sensor information derived from a sensor coupled to the second article; receiving relationship information specifying a relationship between the articles; maintaining first and second virtual articles representing the first article and the second article and sensor information, respectively, and maintaining a context object representing the relationship; recognizing an alert condition relating to the first article; generating updated attribute information; detecting the presence of the first tag at a tag writer station after the alert condition; and causing the tag writer station to write the updated information to the first tag.