Skeleton-Based Structure-Preserving Focus + Context Layout Method of Large Tree

For large trees, a user may only be concerned in a few nodes (e.g., interesting nodes) and their surroundings at a given time. Based on this observation, we present a skeleton-based structure-preserving focus + context layout method. Interesting nodes are considered as the focus, and relationships among interesting nodes (i.e., topological and level relationships) are regarded as context. Based on given interesting nodes, we first employ topology-preserving algorithm to extract a skeleton, which is also a tree, and then use the level-preserving layout algorithm to display the skeleton. Every skeleton node and its surrounding nodes (e.g., parent, sibling, and child nodes) in the original tree are arranged using a tree-map layout algorithm in order for the user to observe the details of the focus. The method was applied to a self-developed probabilistic safety assessment program, named as RiskA, and it performed well in aiding the user back-track the specified nodes during fault tree analysis.