A method, performed by a computer, of facilitating selection by a user of one path from a set of directed paths in an image, partly overlapping but not constituting a directed tree structure, each path beginning at a root and ending at an end point, the method comprising: a) receiving from the user an indication of a specified location in the image; b) identifying a specified path part that best matches the indication of the specified location; and c) suggesting primarily a single path chosen from among two or more paths in the set which include the specified path part, but do not all follow a same route before the specified path part, and at least one of which separates from another path somewhere along its length.