| Abstract: | 整體性限制是資料庫必須遵守的條件,以確保資料的正確性。在本文我們根據正規演繹圖,提出一新的演繹式資料庫整體性限制檢查法。當定義一資料庫時,依據其法則和整體性限制先建立其限制檢查圖,以得出四類不同的元素(Literals),用來簡易地判斷出哪些整體性限制會被目前的更新所影響。假如某一整體性限制會受影響,那麼,本文所提出之檢查法即可依據更新類別(如:加入或刪除事實、法則、或整體性限制)之不同,而施予不同之檢查。本法的優點是它去除了其他現存方法的缺點,例如:只有和受影響的整體性限制相關的隱含更新可被有效地算出,以前所得出的取代可被重複地使用,以及它沒有線性證明程序的低效率問題。
Integrity constraints are conditions that a database is enforced to obey at any time so that it is guaranteed to be in a legal state. In this paper, a new approach for integrity constraint checking in deductive databases is proposed based on the new inference tool of normal deduction graphs. In this method, the constraint checking graph associated with a database is constructed based on the given rules and integrity constraints when the database is defined. Four sets of literals derived from the above graph are then used to detect whether an update affects any integrity constraints in order to avoiding unnecessary checkings. If it does, the proposed checking algorithm is then applied, depending on different update type: the insertion or the deletion of a fact, a rule, or an integrity constraint. The checking method has the advantages that only the implicit updates relevant to the affected integrity constraints are efficiently computed, substitutions obtained before can be reused, and it does not have the inefficiencies of linear proof procedures. |
