Permutation invariance means producing the same output when inputs are rearranged. In graph machine learning, this property matters because node order is not meaningful: the graph’s relationships should determine the result, not how nodes happen to be listed. section 11.3.1
Why graph order should not control an ETA
A route can be represented through connected road segments rather than as independent samples. Congestion on a minor road can influence a main road, while neighboring segments and junctions affect the total travel time. A graph model can use these relationships without treating the node ordering as meaningful. section 11.3.1
Graph convolutional networks apply convolution to each node and its direct neighbors, using the graph structure rather than a regular image grid. A practical PyTorch Geometric example builds a two-layer GCN for the Cora dataset, trains it with node masks, and uses message passing to update node representations. section 11.3.1

