Changwoo Byun

An efficient yet secure XML access control enforcement by safe and correct query modification

This work is a proposal for an efficient yet secure XML access control enforcement which has been specifically designed to support fine-grained security policy. Based on metadata in the DTD, we propose the SQ-Filter which is a pre-processing method that checks on necessary access control rules, and rewrites a users query by extending/eliminating query tree nodes, and by injecting operators that combine a set of nodes from the users query point of view. The scheme has several advantages over other suggested schemes. These include small execution time overhead, and safe and correct query modification. The experimental results clearly demonstrate the efficiency of the approach.

An Efficient Detection of Conflicting Updates in Valid XML

As soon as many users and applications work concurrently on valid XML documents, transaction management for valid XML becomes an important issue. A fundamental problem is the detection of conflicts between operations. The detection of conflicts between operations is very interesting in query optimization for a query compiler and concurrency for a transaction manager. In this paper, we studies the problem of detecting conflicts among XML update operations in the case that input documents are typed by an XML schema (DTD or XML schema). We formalize READ-UPDATE and UPDATE-UPDATE conflicts in valid XML documents, and propose efficient algorithms to detect such conflicts when the update operations are specified using XPath expressions.

OS-DRAM: a delegation administration model in a decentralized enterprise environment

In this paper, we propose an effective delegation administration model using the organizational structure. From a user-level delegation point of view, previous delegation models built on the (Administrative) Role-Based Access Control model cannot present the best solution to security problems such as the leakage of information and the abuse of delegation in a decentralized enterprise environment. Thus, we propose a new integrated management model of administration role-based access control model and delegation policy, which is called the OS-DRAM. This defines the authority range in an organizational structure that is separated from role hierarchy and supports a clear criterion for user-level delegation administration. Consequently, the OS-DRAM supports a decentralized user-level delegation policy in which a regular user can freely delegate his/her authority to other users within a security officers authority range with-out the security officers intervention.

An Optimization Technique for Multiple Continuous Multiple Joins over Data Streams

Join queries having heavy cost are necessary to Data Stream Management System in the sensor network. In this paper, we propose an optimization algorithm for multiple continuous join operators over data streams using a heuristic strategy. First, we propose a solution of building the global shared query execution plan. Second, we solve the problems of updating a window size and routing for a join result. Our experimental results show that the proposed protocol can provide better throughputs than previous methods.