A framework for kernel-based multi-category classification

  • Authors:
  • Simon I. Hill;Arnaud Doucet

  • Affiliations:
  • Department of Engineering, University of Cambridge, Cambridge, UK;Depts. of Statistics and Computer Science, University of British Columbia, Vancouver, Canada

  • Venue:
  • Journal of Artificial Intelligence Research
  • Year:
  • 2007

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Abstract

A geometric framework for understanding multi-category classification is introduced, through which many existing 'all-together' algorithms can be understood. The structure enables parsimonious optimisation, through a direct extension of the binary methodology. The focus is on Support Vector Classification, with parallels drawn to related methods. The ability of the framework to compare algorithms is illustrated by a brief discussion of Fisher consistency. Its utility in improving understanding of multi-category analysis is demonstrated through a derivation of improved generalisation bounds. It is also described how this architecture provides insights regarding how to further improve on the speed of existing multi-category classification algorithms. An initial example of how this might be achieved is developed in the formulation of a straightforward multi-category Sequential Minimal Optimisation algorithm. Proof-of-concept experimental results have shown that this, combined with the mapping of pairwise results, is comparable with benchmark optimisation speeds.