关于D.W.Etherington的扩充产生算法的一个注记

Ｄ．Ｗ．Ｅｔｈｅｒｉｎｇｔｏｎ提出了一类总是有扩充的缺省理论，即有限有序缺省理论，同时使用接连近似的方法给出产生这类缺省理论的所有扩充的算法，并证明该算法对有限有序网络缺省理论总是收敛到一扩充。本文首先举例说明Ｄ．Ｗ．Ｅｔｈｅｒｉｎｇｔｏｎｄ的算法对一般的有限有序缺省理论并非总是收敛，然后给出了该算法对
对一般的有限有序缺省理论收敛的一个充分条件。

Note on D.W.Etherington’s Procedures for Generating Extensions

D.W.Etherington presented a class of default theories called finite ordered default theory,and proposed a procedure to generate all extensions of such default theories.He also proved that this procedure always converges on an extension for finite ordered network theories.In this paper we show by giving an example that D.W.Etherington’s procedure is not convergent for general finite ordered default theories.Moreover,we give a sufficient condition under which the procedure is always convergent for finite ordered default theories.