  The literature in spatial reasoning is extensive; for references to some areas not discussed here, see  Stock 1997,  Kapur &amp; Mundy 1988,  Hammer 1995,  Wilson 1998,  Osherson &amp; Lasnik 1990,  Renz &amp; Nebel 1999,  Yeap &amp; Jeffries 1999,  Forbus et al. 1991,  Chen 1990,  Burger &amp; Bhanu 1992,  Allwein &amp; Barwise 1996,  Glasgow et al. 1995,  and  Kosslyn 1990.  Here, we discuss only one trend, which is closely connected with parallel work in philosophical logic.