Efficient DAG Reachability Query Processing Using Nested Intervals

• Main Authors: Mei-Ling Yu, 余美伶
• Other Authors: Yaw-Huei Chen
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/56286192475447326635

碩士 === 國立嘉義大學 === 資訊工程學系研究所 === 94 === Testing reachability between nodes in a graph is a frequently asked query in many applications that would be modeled using directed acyclic graph (DAG). In order to support efficient reachability testing on DAGs, this thesis devises a new encoding scheme to record the transitive closure information and develops an efficient strategy to test the reachability relationships between nodes. The main idea is to label a spanning tree with numerical intervals first and then generate a transitive closure matrix for the tails and heads of non-tree edges. The existence of a tree edge path between two nodes can be verified by a containment relationship between the label intervals. On the other hand, testing the reachability through both tree and non-tree edges needs to use the numerical intervals to identify the relevant tails and heads and examine their relationships in the transitive closure matrix. The testing operations would be done in constant time, and moreover, the proposed approach supports updates to the underlying graph by locally adjusting the encoding information. In addition, the thesis proposes an access control mechanism that combines role-based and directory-based access control (RBAC and DBAC) mechanisms, and takes the mechanism as an example to test accessible relationships between users and objects, which would have multiple inheritance relationships among them.