Non-linear document navigation, which refers to the process of repeated reading at different levels to overview a document, selective reading to search for useful information within a document, skimming to summarize a document under time constraints, selective bookmark reading in categorized dog-ear markings or referencing between picture/table and the texts related thereof is not well supported on small-screen tablets. This thesis, we proposes a novel method which enables non-linear document navigations via region and direction based touch interaction on both a predefined document structure and chronologically ordered bookmarks after setting up those two different search spaces.
In order to have this non-linear navigation functions for a predefined document structural space, the screen is divided into four vertical sections representing the different structural levels of a document, and dragging in the different sections enables navigating in different levels, from the macro (chapter) to micro (sub-section) levels. Screen-touch interaction via horizontal dragging is used for chronologically ordered bookmarks. Chronologically ordered bookmark space is irrespective of the page order, and this enable us to categorize all the bookmarks by grouping the related ones together although they are separated from each other. In this way, we could minimize repeated touch input and visits to the unnecessary bookmarks.
The implementation of a prototype is introduced, followed by a description of a comparative usability evaluation experiment using typical non-linear navigation tasks performed under time constraints. The experimental results show that the navigation for document structures and chronologically ordered bookmarks via those region- and direction-based touch interactions produced a better performance, higher user satisfaction, and lower usability workload compared with both a conventional structural overview interface and menu-driven user interfaces for bookmarks.