Abstract: Systems and techniques are provided for tracking puts and takes of inventory items by sources and sinks in an area of real space. The system can include sensors producing a plurality of sequences of images of corresponding fields of view in the real space. The system can include image recognition logic, receiving sequences of images from the plurality of sequences. The image recognition logic processes the images in sequences to identify locations of sources and sinks over time represented in the images. The system can include logic to process the identified locations of sources and sinks over time to detect an exchange of an inventory item between sources and sinks.