human: Given a node-centered hypergraph: <hypergraph>, where nodes represent authors and hyperedges represent groups of authors who co-authored the same paper.

Details of the hypergraph:
Center node: "A specification technique based on predicate transformers"
  Abstract: This paper proposes a formal specification technique based on the notion of predicate transformers. Several approaches to showing the completeness are investigated. A method for proving the correctness of an implementation with respect to a formal specification is described.

Connected through hyperedge HE-1 (induced by source paper "Proof techniques for hierarchically structured programs"):
  with members:
    - "An example of hierarchical design and proof"

Question: Please tell me which research area the center author belongs to. The 4 classes are: Computer science, Mathematics, Engineering, Economics, Psychology, Business. Directly output the class name.

gpt: Computer science