Abstract: A computer-implemented method of determining whether digital content has been viewed by a subject, the method including, displaying, by a display device, the digital content to the subject; tracking the gaze of the subject whilst displaying at least a temporal portion of the digital content to acquire tracking data; determining from the tracking data, the display portions of the display device viewed in that temporal portion of the digital content; and generating at least one score by comparing these portions to a predetermined template of display portions for that temporal portion of the digital content; and determining that the subject has viewed at least the temporal portion of the digital content based on the at least one score. A display device and system are also disclosed.

Abstract: A data structure for storing items of information having a time of validity includes a validity interval for each item of information, and methods for making and using the same. The items of information are organized in a data structure having nodes and edges connecting the nodes. This data structure is preferably a directed acyclic graph structure. The data structure includes parent nodes and child nodes. The validity interval specified for any child node generally is contained within the validity interval specified for that child node's parent node, such that the data structure includes no child nodes with a validity interval that falls outside of the validity interval of its parent node.

Abstract: A data structure for storing items of information having a time of life includes a time of life interval for each item of information, and methods for using the same. The items of information are organized in a data structure having nodes and edges connecting the nodes. This data structure is preferably a directed acyclic graph structure. The data structure includes parent nodes and child nodes. The time of life interval specified for any child node generally is contained within the time interval specified for that child node's parent node, such that the data structure includes no child nodes with a time of life interval that falls outside of the time of life interval of its parent node.

Abstract: A data structure for storing items of information having a time of life includes a time of life interval for each item of information, and methods for using the same. The items of information are organized in a data structure having nodes and edges connecting the nodes. This data structure is preferably a directed acyclic graph structure. The data structure includes parent nodes and child nodes. The time of life interval specified for any child node generally is contained within the time interval specified for that child node's parent node, such that the data structure includes no child nodes with a time of life interval that falls outside of the time of life interval of its parent node.

Abstract: A data structure for storing items of information having a time of life includes a time of life interval for each item of information. The items of information are organized in a data structure having nodes and edges connecting the nodes. This data structure is preferably a directed acyclic graph structure. The data structure includes parent nodes and child nodes. The time interval specified for any child node must always be contained within the time interval specified for that child node's parent node, such that the data structure includes no child nodes with a time of life interval that falls outside of the time of life interval of its parent node.