The challenge of flow mapping is to reduce the 'spaghetti-effect' related to the overlapping of sometimes too many graphic ties. The conventional solution aims to 'select' them with 'parsimony.' Several approaches are possible depending on the way the selection is processed: on the graphical aspects, the cartographical one or during the pretreatment data step. Statistical and algebraic analysis-applied to mapping- consider 'selection' as a way to 'reduce' the universe of data especially by the production of indexes. We propose an extension of the flow matrix algebra approach, implemented by Tobler (1979, 1982), toward a logical reasoning. Three operations from the combination of logical operators are proposed as alternative commonly indices used in flow mapping. Their effectiveness is presented through an implementation on a matrix of internal migration.
