Let $C$ and $D$ be simplicial complexes. A simplicial map is a map $f : C \to D$ such that for any face $F \subset C$, we have that $f(F)$ is contained in a face of $D$.
To specify a map of simplicial complexes, the target and source complexes need to be specified as well as a matrix which determines a map between the complexes' corresponding rings.
The primary constructor of a simplicial map is map(SimplicialComplex,SimplicialComplex,Matrix).
The object SimplicialMap is a type, with ancestor classes HashTable < Thing.