The computer-assisted authoring of mathematical documents using a scientific text-editor requires new mathematical knowledge management and transformation techniques. The challenge is that, throughout an assistance system like the ΩMEGA system, various kinds of given and derived knowledge units occur in different formats and with different dependencies. If changes occur in these pieces of knowledge, they need to be effectively propagated.We present a Change-Oriented Architecture for mathematical authoring assistance. This work includes an efficient method for the computation of weighted semantic changes and an invertible grammar formalism for the automated bidirectional transformation between interface documents. The presented architecture provides an adequate basis for the computer-assisted authoring of mathematical documents with semantic annotations and a controlled mathematical language.