An inventory location, such as a shelf, may be used to stow different items. The shelf is divided into a plurality of adjacent lanes, some of which may be grouped into a cluster. Items are placed upon the lanes of the cluster. Each lane includes one or more weight sensors to obtain weight data about a load on the lane. Based on the weight data and physical layout data for the shelf, one or more hypotheses may be determined for describing interactions, such as a pick or place of an item, occurring at the lanes of a cluster. One of the hypotheses may be selected as a solution for describing the interaction and used to maintain inventory quantities of items at the shelf.