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ShrinkTree is a compaction algorithm that maintains the topology of a layout. The relocation of diagram elements is based on contracting a spanning tree.
The algorithm uses the programmatic structure of SPOrE, which stands for Structure, Processing Order, and Execution.
The structure phase extracts geometric information from the given layout to capture the topology that should be preserved during the subsequent adjustment of the layout.
For this purpose, a Delaunay triangulation is implemented, which captures proximity information.
Now, the processing order for the last phase is determined and represented by a tree.
The execution phase traverses the previously constructed tree and applies an algorithm specific operation to each node.
The functional principle is based on a modification of an overlap removal algorithm presented by Nachmanson et al. in “Node overlap removal by growing a tree”. First, the set of vertices corresponding to the nodes’ centers is Delaunay triangulated. Second, a spanning tree of the triangulation edges is constructed. Third, the spanning tree is shrunk pulling the nodes closer together.
Compacting the inclusion tree of a hierarchical Ptolemy model:
|Cost Function for Spanning Tree
|Root node for spanning tree construction
|Root selection for spanning tree
|Structure Extraction Strategy
|Tree Construction Strategy
|Underlying Layout Algorithm