human: Given a node-centered hypergraph: <hypergraph>, where nodes represent papers and hyperedges represent groups of papers sharing a common citing paper.

Details of the hypergraph:
Center node: "A Six-Point Condition for Ordinal Matrices  keywords: additive, algorithm, evolution, ordinal, phylogeny"
  Abstract: Ordinal assertions in an evolutionary context are of the form "species s is more similar to species x than to species y" and can be deduced from a distance matrix M of interspecies dissimilarities (M [s; x] &lt; M [s; y]). Given species x and y, the ordinal binary character c xy of M is defined by c xy (s) = 1 if and only if M [s; x] &lt; M[s; y], for all species s. In this paper we present several results concerning the inference of evolutionary trees or phylogenies from ordinal assertions. In particular, we present A six-point condition that characterizes those distance matrices whose ordinal binary characters are pairwise compatible. This characterization is analogous to the four-point condition for additive matrices. An optimal O(n 2 ) algorithm, where n is the number of species, for recovering a phylogeny that realizes the ordinal binary characters of a distance matrix that satisfies the six-point condition. An NP-completeness result on determining if there is a phylogeny that realizes k or more of the ordinal binary characters of a given distance matrix.

Connected through hyperedge HE-1 (induced by source paper "99-113. Construction of Phylogenetic Trees, Science, Fitting the Gene Lineage Into Its Species Lineage. A"):
  with members:
    - "Inserting the best known bounds for weighted bipar tite matching [11], with 1=2 p polynomial-time"

Question: Please tell me which class the center node belongs to. The 7 classes are: Neural_Networks, Reinforcement_Learning, Probabilistic_Methods, Theory, Genetic_Algorithms, Case_Based, Rule_Learning. Directly output the class name.

gpt: Theory