Conceptually it is easiest to think of route-finding as the function which finds the shortest path through a network from a nominated Start point to a nominated Finish point.
Basically the operation determines which series of links, based on their individual lengths, will form the shortest path through the network, i.e. the shortest of all possible routes from start to finish.
However, this is only one application of the route-finding algorithm. Thinking in the abstract, we replace ‘distance’ with ‘cost’ to find the ‘least-cost’ path through a network where ‘cost’ can be any quantifiable attribute of a link.
This opens many possibilities. To find the quickest path through a network one could factor link type, average speed and link length into the equation, e.g. you can define 70mph for Motorways, 50mph for A-Roads, etc. and find the quickest path through an ITN network.
The key to this is that the 'cost' of a link is determined by an expression. The routing function will apply this expression to every link to determine its cost and on the basis of those costs will find the least-cost, or optimum, path through the network, e.g. shortest, quickest, 'prettiest' etc.
The only imperatives are:
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