2.2.4 Reaction
representation
Reaction representation directly affects the accuracy of the model
prediction. In this work, a new
condensed hypergraph reaction
descriptor is proposed consisting of graph adjacency matrix and feature
matrix. Graph adjacency matrix is used to describe the connection of
nodes. It consists of reaction mapping graph, reaction agent graph,
molecular/reaction node and reaction summary node (Fig.1(b) ).
Reaction mapping graph is constructed by the union of reactants and
products graph. It considers the reaction atom transfers which provides
more features for model prediction than directly splicing of molecules
descriptors. Reaction agent graph uses graph data structure to represent
reaction agents. In order to consider the influence between reactions
and reaction agents, molecules and reaction nodes are connected to each
other via bidirectional edges, enabling the message passing between
reaction and agent graphs. Accompanied by bidirectional edge connections
of reaction nodes and molecular nodes, the message transfer between
reaction mapping graph and agent graphs are achieved. Accompanied by
uni-directional edge connections of molecules and reaction nodes to
reaction summary nodes, reaction features are aggregated from molecules
to the whole reaction.
Node feature matrix is composed of atomic features which can be
classified as indicators and change sites. Indicator sites primarily
display the type of atoms, while change sites integrate the features
from reactants and products to illustrate the changes in atom properties
during the reactions. Edge feature matrix is composed of bond features.
It is exclusively constructed by the change sites. By comparing of the
bond features of the reactants and products, the changes of bond
properties become clear, allowing for a clear differentiation between
the directions of reversible reactions. The type of atom features and
bond features are listed in Table 1 .