Hi,
Dr. Y. Xiang is the founder and primary investigator of the theory
of "pseudo-independent" domains that causes failure of commonly used 
algorithms for learning belief networks from data due to their single-
link-lookahead search method.  You can see the full list of the 
papers dealing with this issue at his homepage where you can download
most of them: 
  http://snowhite.cis.uoguelph.ca/~yxiang/
The following is the reference to some:
Y. Xiang, S.K.M Wong and N. Cercone. "Critical Remarks on Single 
Link Search in Learning Belief Networks." In Proc. Uncertainty in 
Artificial Intelligence 96, 564-571, 1996. 
Y. Xiang, "A characterization of single-link search in learning 
belief networks," in Proc. Pacific Rim Knowledge Acquisition 
Workshop, 218-233, Singapore, 1998.
Y. Xiang, J. Hu, N. Cercone and H. Hamilton, "Learning 
Pseudo-Independent Models: Analytical and Experimental Results", 
Proc. AI 2000, In H. Hamilton, editor, Advances in Artificial 
Intelligence, 227-239, Springer, 2000. 
Hope this helps.
Jae
On Fri, 6 Apr 2001 R.G.Cowell@city.ac.uk wrote:
> Several Bayes net structure learning algorithms work incrementally by
> testing the addition of a single link to a current model , seeing if
> it improves some score, such as marginal likelihood, and then
> selecting the link which increases the score the most. I remember that
> there were some papers a few years back pointing out that this
> single-link look-ahead search fails for some special situations and
> the simultaneous addition of two links should be considered instead,
> but I cannot recall any details of the papers.
> 
> I would be grateful if anyone can provide references to papers which
> deal with this issue.
> 
> Thanks in advance.
> 
> 
> 
> Robert Cowell
> Department of Actuarial Science and Statistics
> City University
> Northampton Square
> London EC1V 0HB
>  
> tel: (44) 020 7477 - 8454
> fax  (44) 020 7477 - 8838
> www: http://www.staff.city.ac.uk/~rgc
> 
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