The idea behind local regions is strongly connected to that of standard regions, but from the
top-down perspective. As an example: in standard regions, we only had to consider one type of
triangle, the one that is straight-sided, right-angled, and whose principle horizontal and
vertical sides where aligned with the coordinate axes. Of course, meshes of elements consist of
elements that may are may not be right-angled, planar-sided, etc. The starting point for us is
the question of how to build build basis functions that exist of a world-space element –
that is, an element whose vertex positions lie in the engineering (PDE) coordinate
system of interest. Such an expansion is a local region. In *Nektar++*, each local
region is-a standard region and has-a spatial domain data structure. The local region
inherits common expansion methods from its standard region parent, and it uses
its spatial domain information to specialize its operators to its local coordinate
system.