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 structure from manipulation for text-graphic objects"
  Abstract: The general purpose graphics systems of the future will need a simple logic for visual objects—one structure underlying both text and graphics. As an experiment, perhaps the immediate handling of visual objects by the user can provide the starting point for developing that structure. This paper describes the PAM graphics system, in which  the structure of text-graphic objects arises directly out of manual manipulation.  The needs of manual manipulation determine the  text-graphic pattern  as the simplest organizing structure for images; PAM stands for  P Attern  M anipulating. The PAM system is designed for the agile manipulation of text-graphic patterns—first manually, and then, later, programmatically.   Starting from this strict 'front-in' viewpoint—where immediate manipulation (hand powered animation) was to be the primary application—a 'manipulative grammar' was evolved to give the user a simple yet powerful handle on text-graphic images. This grammar turned out to be a generalization of LISP syntax from textual symbolic expressions to text-graphic forms, structuring such forms as trees and then offering:

Connected through hyperedge HE-1 (induced by source paper "Computing with text-graphic forms"):
  with members:
    (none)

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