完全・不完全知識を扱う高水準論理型データべースの自己組織化

抄録

In this paper, we discuss a self organization mechanism of ALDB (Advanced Logical DataBase) that is capable of handling the complete-incomplete knowledge. A number of exceptional data will be included as a DB gets larger. The knowledge including exceptions can be considered as the incomplete knowledge, because it may derive inconsistency. For logical DB, the occurence of inconsistency will be crucial. Therefore, in order to maintain the consistency of DB, some self organization mechanism should be developed. We propose the self organization mechanism (SOM) of ALDB which is realized by transforming the complete knowledge into the incomplete knowledge. The ALDB consists of extensional DB (EDB), complete intensional DB (CIDB) and incomplete intensional DB (IIDB). EDB is a set of facts, whereas CIDB and IIDB are sets of rules representing complete knowledge and incomplete knowledge, respectively. The data retrieved from the ALDB is concerned with the ALDB extension that is a set of derived conclusions. The SOM is divided into the three steps : 1) the check of consistency, 2) the selection of a rule to be transformed and 3) the transformation to an incomplete rule and its ordering. When new data is added into the ALDB, the SOM firstly checks the consistency by investigating only the part of complete knowledge with the use of SLD resolution technique. If the ALDB is inconsistent, the SOM identifies a complete rule that is logically false by contradiction backtracking algorithm. The selected rule is then transformed to an incomplete rule whose intended meaning is "If…, then normally…". It allows the exceptions that are not satisfied with a complete rule. Finally, the SOM makes the ordering among the incomplete rules based on the generality of each rule. The ordering plays a significant role to reduce the number of ALDB extensions.