Why are some non-contiguous polylines or polygons “joined together” after I do an overlay operation in XTools?
You are seeing what are called “multipart shapes”. By default in ArcView, multipart shapes are created under certain conditions when intersecting shapes. A multipart shape is like a region in ArcInfo. Multipart shapes are not a problem for display and for most analysis. The only time they would be a problem is if you need to edit the attributes or spatial location of one part of a multipart shape, or if you need to know the sizes of individual parts of the shape. For that possibility, I included a tool named “Convert Multipart Shapes to Single Part” in the View XTools menu. This script allows you to break the multipart shapes into single part shapes. In addition to the XTools overlay tools, multipart shapes are created by the Edit, Union Features menu option in the standard ArcView user interface. An example of multipart shapes can be found in the ESRI sample data. The state of Alaska in the states.shp shapefile is one example. Alaska has only one record in its table, but it has 32 par
