The idea is that given an appropriate string-oriented language to express the components of a mixture, one can assemble mixtures lexically. We then use string-processing tools to manipulate the mixtures.
The "chemical reactions" used to build mixtures are effectively reduced to simple connections of adjacent monomers.
Since monomers typically map back to individual reagents, part of the chemistry is lost.
A transformation represents a compact way to represent and manipulate molecules and their relationship to the monomers in the database.