Integration and efficient lookup of compressed XML accessibility maps

XML is emerging as a useful platform-independent data representation language. As more and more XML data is shared across data sources, it becomes important to consider the issue of XML access control. One promising approach to store the accessibility information is based on the CAM (compressed accessibility map). We make two advancements in this direction: 1) Previous work suggests that for each user group and each operation type, a different CAM is built. We observe that the performance and storage requirements can be further improved by combining multiple CAMs into an ICAM (integrated CAM). We explore this possibility and propose an integration mechanism. 2) If the change in structure of the XML data is not frequent, we suggest an efficient lookup method, which can be applied to CAMs or ICAMs, with a much lower time complexity compared to the previous approach. We show by experiments the effectiveness of our approach.