This concept appears in ICOCO API. A field template is the adequate data structure to perform costly interpolation matrix computation as Remapper class does. A field template can be seen as field without its double values. The double values are only used for light matrix vector multiplication.

Concretely a field template is a pair containing :

a mesh
a spatial discretization (on cells, on nodes, on Gauss points (including localizations, reference elements), )

TODO enhance here