Chapter Preview: Navigating Trees, Hierarchical Data, and CyclesSeeing Hierarchies and Nested Data: Three ExamplesHierarchical Data in a Bill of MaterialsHierarchical Data in Version Control SystemsHierarchical Data in Self-Organizing NetworksWhy Graph Technology for Hierarchical Data?Finding Your Way Through a Forest of TerminologyTrees, Roots, and LeavesDepth in Walks, Paths, and CyclesUnderstanding Hierarchies with Our Sensor DataUnderstand the DataConceptual Model Using the GSL NotationImplement SchemaBefore We Build Our QueriesQuerying from Leaves to Roots in DevelopmentWhere Has This Sensor Sent Information To?From This Sensor, What Was Its Path to Any Tower?From Bottom Up to Top DownQuerying from Roots to Leaves in DevelopmentSetup Query: Which Tower Has the Most Sensor Connections So That We Could Explore It for Our Example?Which Sensors Have Connected Directly to Georgetown?Find All Sensors That Connected to GeorgetownDepth Limiting in RecursionGoing Back in Time