  Architectural transformations play a key role in the evolution of complex
systems, from design algorithms for metamaterials to flow and plasticity of
disordered media. Here, we develop a general framework for the evolution of the
linear mechanical response of network structures under discrete architectural
transformations via sequential removal and addition of elastic elements. We
focus on a class of spatially complex metamaterials, consisting of triangular
building blocks. Rotations of these building blocks, corresponding to removing
and adding elastic elements, introduce (topological) architectural defects. We
show that the metamaterials' states of self stress play a crucial role, and
that the mutually exclusive self stress states between two different network
architectures span the difference in their mechanical response. For our class
of metamaterials, we identify a localized representation of these states of
self stress, which allows us to capture the evolving response. We use our
insights to understand the unusual stress-steering behaviour of topological
defects.
