  The issue also relates to the question of whether there can be extended mereological simples (raised by van Inwagen 1981 and Lewis 1991: 32, 76 and extensively discussed e.g. in Markosian 1998, Parsons 2000, Simons 2004, Braddon-Mitchell and Miller 2006, and McDaniel 2007, inter alia). For the characterization of boundaries as lower-dimensional extremities is compatible with the possibility that a boundary's spatiotemporal extension transcend its mereological structure. A pointy boundary, for instance, could be pointy in that it has no proper parts, but that does not rule out that it be located at an extended region short of assuming that the mereological structure of a thing always matches perfectly that of its location (what Varzi 2007:1018 calls “mirroring” and Shaffer 2009:138, Uzquiano 2011 “harmony”).