Using either QGIS (1.9) or ArcInfo (9.3.1) I'm trying to identify unique overlaps of prehistoric building footprints from an archaeological site recorded within a single polygon shapefile. While the Overlay>Interset and Geoprocessing>Intersect tools in ArcInfo and QGIS, respectively, work to some degree both return multiple results for each unique overlap. An appropriate parallel for my problem I suppose can be illustrated by a simple 3 unit Venn diagramme in which there are 3 unique intersections or overlaps, yet when running an Intersect routine (particularly that in ArcInfo) I often get up to 12 unique polygons returned - 2 for each shared 'leaf-shaped' intersection, and a further 6 for the centre overlap (each intersection being counted twice).
I'm trying to produce a shapefile illustrating those unique intersections. Ideally I would love for the attribute table of this produced shp to contain details of each intersection i.e. Feature_X intersects with Feature_Y, but I fear I may be asking for the moon on a stick.
Many thanks in advance for any and all advice, Marc
Edit: Following the excellent suggestion of @PolyGeo, I have attached a rough sketch below to hopefully better illustrate my current problems and what I'm hoping to achieve. Forgive the hand-drawn sketch, I'm away from my main PC.