The `SEGMENTS` section contains an arbitrary number of segments and
(optionally) boundaries. In turn each segment contains an arbitrary number of
grids and attributes. Each attribute references exactly one grid, but not every
grid must have an associated attribute. The semantical predicate "*{dim
== X}?*" is used to distinguish elements of different geometrical
dimension. Fig. B.5 depicts the syntax of the `SEGMENTS` section.

2003-03-27