In the recent past a number of exotic ontology related  to  space
and time have been explored by researchers. For example, a set of
region-connection calculi (RCC-5,  RCC-8),  cyclic-time  algebra,
partially-ordered  time  algebra,  Cardinal algebra with point in
2D space, etc. are being  developed.  They  often  show    strong
simiarity     amongst  themselves   and   with   the  traditional
algebras (point, interval, duration  etc.)   of   spatio-temporal
constraints.   From   a   broad  perspective  they seem to form a
group of constraint algebra where the domain  is  continuous.  We
would  like  to  understand   all  these diferent algebras from a
broad perspective. For example, we would like to  know  if  there
exists  any  common properties between the tractable sub-algebras
of these algebras. It appears that we need a different type of 
geometry to understand the qualitative 'space.'