G. Wang et al. (Eds.): RSKT 2006, LNAI 4062, pp. 28
–
30, 2006.
© Springer-Verlag Berlin Heidelberg 2006
Hierarchical Machine Learning – A Learning
Methodology Inspired by Human Intelligence*
Ling Zhang
1
and Bo Zhang
2
1
Artificial Intelligence Institute, Anhui University
Hefei, China 230039
[email protected]
2
Computer Science & Technology Department, Tsinghua University
Beijing, China 100084
[email protected]
Abstract. One of the basic characteristics in human problem solving, including
learning, is the ability to conceptualize the world at different granularities and
translate from one abstraction level to the others easily, i.e., deal with them
hierarchically[1]. But computers can only solve problems in one abstraction level
generally. This is one of the reasons that human beings are superior to computers
in problem solving and learning. In order to endow the computers with the
human’s ability, several mathematical models have been presented such as fuzzy
set, rough set theories [2, 3]. Based on the models, the problem solving and
machine learning can be handled at different grain-size worlds. We proposed a
quotient space based model [4, 5] that can also deal with the problems
hierarchically. In the model, the world is represented by a semi-lattice composed
by a set of quotient spaces: each of them represents the world at a certain
grain-size and is denoted by a triplet
(,,)XFf , where X is a domain, F- the
structure of X, f -the attribute of X.
In this talk, we will discuss the hierarchical machine learning based on the
proposed model. From the quotient space model point of view, a supervised
learning (classification) can be regarded as finding a mapping from a low-level
feature space to a high-level conceptual space, i.e., from a fine space to its
quotient space (a coarse space) in the model. Since there is a big semantic gap
between the low-level feature spaces and the conceptual spaces, finding the
mapping is quite difficult and inefficiency. For example, it needs a large number
of training samples and a huge amount of computational cost generally. In order
to reduce the computational complexity in machine learning, the characteristics
of human learning are adopted. In human learning, people always use a
multi-level learning strategy, including multi-level classifiers and multi-level
features, instead of one-level, i.e., learning at spaces with different grain-size.
We call this kind of machine learning the hierarchical learning. So the
hierarchical learning is a powerful strategy for improving machine learning.
Taking the image retrieval as an example, we’ll show how to use the
hierarchical learning strategy to the field. Given a query (an image) by a user, the
*
This paper is supported by the National Science Foundation of China Grant No. 60321002,
60475017, the National Key Foundation R & D Project under Grant No. 2004CB318108.