Transit node routing: Difference between revisions

Revision as of 01:33, 12 October 2020

Revision as of 22:02, 28 November 2020

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'''Which locality filter should be used?'''

If the highest node of a shortest up-down-path in the hierarchy is not part of the set of transit nodes, then the query was local. This implies that neither the up-part of the path (beginning at the starting node) nor the down-part of the path (ending at the target node) can contain a transit node and there must be a common node in both paths. During the calculation of the access nodes, the [[search space]]{{dn|date=August 2019}} (all visited nodes towards the top of the hierarchy) for each node can be stored without including transit nodes. When performing a query, those search spaces for start- and target node are checked for an intersection. If those spaces are [[Disjoint sets|disjoint]], transit node routing can be used because the up- and down-paths must meet at a transit node. Otherwise there could be a shortest path without a transit node.

'''How should local queries be handled?'''