Abstract: A presentation system capable of detecting one or more gestures and contacts on a touch sensitive display. The presentation system can display indicia of such contacts, such as when a user writes with a fingertip, and can remove or alter such indicia responsive to other gestures and contacts. The system can accurately distinguish between types of gestures detected, such as between a writing gesture and an erasing gesture, on both large and small touch sensitive displays, thereby obviating the need for a user to make additional selective inputs to transition from one type of gesture to another.

Abstract: Techniques of preserving annotation relationships are disclosed. The techniques are used a presentation system comprising at least one display, at least one processor coupled to the display, and a memory storing instructions, the instructions comprising instructions executable by the processor to display content on the display based on a content location, receive an annotation, group the annotation into an annotation group, determine the annotation group is related to the content based on the location of the annotation group and the content location, associate the annotation group with the content based on the determination, receive an indication of a change in the content location of the content, adjust the annotation group based on the change in the content location of the content, and display content based on the change in the content location and the adjusted annotation group.