routing method for computing routes over uncertain geo - spatial data whereby only upon visiting the geographic entities it can be determined whether the needed service or product is actually provided and is adequate . when dealing with uncertain data , the returned route may need to go via several entities of the same type . another routing method consists of finding an efficient and effective route from a starting point to an ending point going trough a predetermined number of objects , wherein each object represents a geographical entity of a unique type , and each object is selected from a distinct set of similar objects .