Federated Multitask Learning with Manifold Regularization for Face Spoof Attack Detection

Table 2

Definition of notations in the hypergraph regularization.

Name	Definition
	Vertices in the hypergraph
	The label of the vertex
	Edges in the hypergraph
	The weight of an edge
	The degree of an edge, . It illustrates how many vertices are connected by . In traditional graph representation, .
	The degree of a vertex . It is calculated by summing the weighting values of edges connected to this vertex.
	The diagonal matrix containing the vertex degrees
	The diagonal matrix containing the edge degrees
	In this matrix, if
	The diagonal matrix containing the weights of hyperedges
	The set of labels
	The set of vertices
	The set of edges