  In this paper, we introduce a generalized topological quantum field theory
based on the symmetric monoidal category which we call causal network
condensation since it can be regarded as a generalization of spin network
construction of Baez, Turaev-Viro model and causal set theory. In this paper we
introduce some new concepts, including causal network category, causal network
diagrams, and their gauge transformations. Based on these concepts, we
introduce the nerve functor for the symmetric monoidal category. It can be
regarded as a generalization of the nerve functor for simplicial category.
