Rewriting Structured Cospans

To support the study of compositional networks, we further develop the formalism of structured cospans. To enable rewriting, we introduce a category whose objects are structured cospans and characterize conditions under which this category is a topos or is adhesive. We then define a structured cospan grammar and language, using a 2-category framework. As an application, we demonstrate that for various sorts of graphs, hypergraphs, and Petri nets, any grammar induces the same language as its corresponding discrete grammar. This result allows us to extend the inductive perspective of rewriting to these structures.