用对分HS-树计算最小碰集

在基于模型的诊断中,利用冲突集计算最小碰集是其关键的步骤,因为所有冲突集的最小碰集就是所考察系统的诊断.在Reiter的方法中,要用HS-树(图)来计算最小冲突集的最小碰集.HS-树的计算量比较大,且又会因为剪枝的问题而剪掉真实解.提出了用对分HS-树(binary hitting set-树,简称BHS-树)计算最小碰集的方法.这种方法的优点是:(1)产生的树的节点数明显少于HS-树,因而效率较高;(2)解决了因为剪枝而产生的最小碰集丢失的问题;(3)在新增加冲突集时不必完全重新计算,只需在原BHS-树

Computing the Minimal Hitting Sets with Binary HS-Tree

In the model-based diagnosis, a key step is to compute the minimal hitting sets from the minimal conflict sets, because the minimal hitting sets of all the conflict sets are the faults of an investigated system. In Reiter s method, HS-tree is used for computing the minimal hitting sets. However, it will need a heavy work, and will result in the fact that the correct hitting sets are probably pruned away. In this paper, a new method is put forword for computing minimal hitting sets by the "binary hitting set tree", in brief, BHS-tree. This method will improve Reiter's approaches in the aspects as follows. (1) The number of BHS-tree nodes is apparently less than that of HS-tree; (2) As a result of being pruned, the loss of the minimal hitting sets will not produce; (3) When the new conflict sets are inserted, it is unnecessary to rebuild BHS-tree, instead, just adding the new branches to the BHS-tree. This property is extraordinarily useful for the actual diagnosis. Thus, the BHS-tree method is analyzed and verified in theory and the given programs are tested.