Selection is a critical task in document processing systems, and is required for many manipulation operations such as deleting, moving, reusing, or re-formatting. Documents have usually a hierarchical structure. For example, books are naturally represented as a sequence of chapters, sections, subsections and so on until described completely in terms of basic component such as paragraphs, tabular material, and images. This structure is usually visualized using different formats (e.g. font sizes) or different views (e.g. outline views in Microsoft Words). Despite this inherent structure, to the best of our knowledge no selection technique systematically utilizes this structure in pen-based system. The multi-click approach is a standard selection method offered by many systems. Single, double, and triple clicking then selects the corresponding unit (e.g. word, line, and paragraph, respectively). This approach cannot select larger units than a paragraph and is not well suited for pen-based systems, as multi-clicking is unreliable for pens. Current selection techniques such as Rectangle, Lasso require users to explicitly define a selection scope by a pen movement. This can be time-consuming and error-prone when the target is large (e.g. multiple paragraphs) or spans more than a page. In the later case, the user has to select and scroll simultaneously. Moreover, these techniques are one directional, i.e. from the start point to the end point. The following common scenario describes potential problems: during a paragraph selection, the user decides to select the previous paragraph as well. She has two choices: either cancelling, relocating the mouse (pen), and re-starting a new selection, or selecting both paragraphs individually while using a phrasing technique (such as a Shift-key).
We propose a novel pen-based technique issues for selecting document components. Performing a pigtail gesture in a margin selects the nearby unit. Continuous pigtails extend selection to previous, next or both units according to the last pigtail orientation. Our technique automatically scrolls (or zooms out) when selecting off-screen targets.