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Machine Learning - DISCo

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Height (Joe, Short) Height(Sue, Short)<br />

Nationality(Joe, US) Nationality(Sue, US)<br />

Mother(Joe, Mary) Mother(Sue, Mary)<br />

Age (Joe, 8) Age(Sue, 6)<br />

The following domain theory is helpful for acquiring the HouseMates<br />

concept:<br />

HouseMates(x, y) t InSameFamily(x, y)<br />

HouseMates(x, y) t FraternityBrothers(x, y)<br />

InSameFamily(x, y) t Married(x, y)<br />

InSameFamily (x, y) t Youngster(x) A Youngster (y) A SameMother (x, y)<br />

SameMother(x, y) t Mother(x, z) A Mother(y, z)<br />

Youngster(x) t Age(x, a) A LessThan(a, 10)<br />

Apply the PROLOG-EBG algorithm to the task of generalizing from the above<br />

instance, using the above domain theory. In particular,<br />

(a) Show a hand-trace of the PROLOG-EBG algorithm applied to this problem; that<br />

is, show the explanation generated for the training instance, show the result of<br />

regressing the target concept through this explanation, and show the resulting<br />

Horn clause rule.<br />

(b) Suppose that the target concept is "people who live with Joe" instead of "pairs<br />

of people who live together." Write down this target concept in terms of the<br />

above formalism. Assuming the same training instance and domain theory as<br />

before, what Horn clause rule will PROLOG-EBG produce for this new target<br />

concept?<br />

As noted in Section 11.3.1, PROLOG-EBG can construct useful new features that are<br />

not explicit features of the instances, but that are defined in terms of the explicit<br />

features and that are useful for describing the appropriate generalization. These<br />

features are derived as a side effect of analyzing the training example explanation. A<br />

second method for deriving useful features is the BACKPROPAGATION algorithm for<br />

multilayer neural networks, in which new features are learned by the hidden units<br />

based on the statistical properties of a large number of examples. Can you suggest<br />

a way in which one might combine these analytical and inductive approaches to<br />

generating new features? (Warning: This is an open research problem.)<br />

REFERENCES<br />

Ahn, W., Mooney, R. J., Brewer, W. F., & DeJong, G. F. (1987). Schema acquisition from one<br />

example: Psychological evidence for explanation-based learning. Ninth Annual Conference of<br />

the Cognitive Science Society (pp. 50-57). Hillsdale, NJ: Lawrence Erlbaum Associates.<br />

Bennett, S. W., & DeJong, G. F. (1996). Real-world robotics: <strong>Learning</strong> to plan for robust execution.<br />

<strong>Machine</strong> kaming, 23, 121.<br />

Carbonell, J., Knoblock, C., & Minton, S. (1990). PRODIGY: An integrated architecture for planning<br />

and learning. In K. VanLehn (Ed.), Architectures for Intelligence. Hillsdale, NJ: Lawrence<br />

Erlbaum Associates.<br />

Chien, S. (1993). NONMON: <strong>Learning</strong> with recoverable simplifications. In G. DeJong (Ed.), Znvestigating<br />

explanation-based learning (pp. 41M34). Boston, MA: Kluwer Academic Publishers.<br />

Davies, T. R., and Russell, S. J. (1987). A logical approach to reasoning by analogy. Proceedings of<br />

the 10th International Joint Conference on ArtiJcial Intelligence (pp. 264-270). San Mateo,<br />

CA: Morgan Kaufmann.

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