Sif provides dynamic, extensible costing for edges and transitions between edges (turn costs). Its primary use is in the routing engine when forming the best path between locations. In keeping with the Norse mythological theme, the name Sif was chosen since Sif is a companion to Thor.
Sif is essentially a set of various data structures and alogrithms which deal with things like: correlating an input location to the underlying graph, partial distance along an edge and filtering edges which shouldn't be considered for correlation.
What follows are some notable components of sif.