Meghdad Mirabi

An Access Control Model for Supporting XML Document Updating

Recently, specifying access control for XML documents over World Wide Web have been proposed. Most of the proposed models for specifying XML access control only support read privilege. Therefore, offering an access control model considering update operations is a challenging issue in XML access control specification. This paper proposes an XML access control model to specify access authorizations which deal with updating the well-formed XML documents. Also, a formal representation of update operations supported by our proposed model is defined in terms of the different policies which are taken for each update operation.

PS+Pre/Post

XML data broadcast is an efficient way to disseminate XML data to a large number of mobile clients in mobile wireless networks. Recently, several indexing methods have been proposed to improve the performance of XML query processing in terms of access time and tuning time over XML streams. However, existing indexing methods cannot process twig pattern XML queries. In this paper, we propose a novel structure for streaming XML data called PS+Pre/Post by integrating the path summary technique and the pre/post labeling scheme. Our proposed XML stream structure exploits the benefits of the path summary technique and the pre/post labeling scheme to efficiently process different types of XML queries over the broadcast stream. Experimental results show that our proposed XML stream structure improves the performance of access time and tuning time in processing different types of XML queries.

An energy conservation indexing method for secure XML data broadcast in mobile wireless networks

Secure broadcasting of XML data is becoming an essential requirement for many applications in mobile wireless networks. Several indexing methods have been proposed to reduce the tuning time in processing the XML queries over the wireless XML stream. Tuning time is the sum of period of times which a mobile client stays in active mode in order to retrieve the required data over the wireless stream. Therefore, it is frequently used to estimate the energy consumption of a mobile client. The problem of existing indexing methods is that they cannot directly be applied to an encrypted XML stream since mobile clients can only access the authorized parts of the XML data in an encrypted XML stream. In this paper, we define a unit structure of an XML stream called SecNode which guarantees confidentiality of the XML data in the wireless stream. We also define two indexes called Min (NCS) and Min (NIS) for the SecNode structure based on the set of access authorizations specified in the original XML document in order to efficiently process the XML queries over the encrypted XML stream. Experimental results show that the use of the SecNode structure for secure XML data broadcast improves the performance of XML query processing in terms of tuning time and therefore reduces the power consumption at mobile clients.

Integrating Access Control Mechanism with EXEL Labeling Scheme for XML Document Updating

Recently, an urgent need for XML access control mechanism over World Wide Web has been felt. Moreover, an efficient dynamic labeling scheme is required in order to eliminate the re-labeling process of existing XML nodes during XML document updating. However, the previous research on access control mechanisms for XML documents has not addressed the issue of integrating access control with a dynamic labeling scheme. In this paper, we propose an XML access control mechanism integrated with EXEL encoding and labeling scheme to eliminate the re-labeling process for updating the well-formed XML documents. The key idea is to regard an authorization as a query condition to be satisfied. Therefore, the benefit of speeding up searching and querying processes is obtained by employing such a labeling scheme in our proposed access control mechanism.

Label Size Increment of Bit String Based Labeling Scheme in Dynamic XML Updating

XML query processing based on labeling schemes has been proposed in the past several years. Based on labeling schemes, the structural relationships between XML nodes can be directly determined without the need of accessing the XML document. However, the existing labeling schemes have to re-label the pre-existing XML nodes or re-calculate the label values when a new node is inserted into the XML tree during an updating process. EXEL as a bit string based encoding and labeling scheme is able to remove the process of re-labeling for the pre-existing XML nodes efficiently. However, EXEL is unable to reuse the deleted labels for future node insertions. Also, another problem of EXEL is in the frequent skewed insertions where nodes always are inserted at a fixed place of an XML tree. In this case, the label size increases significantly. In this paper, we propose an algorithm to reuse the deleted labels for future node insertions and propose a strategy to solve the problem of frequent skewed insertion. The experimental results show that the proposed algorithm can reuse all the deleted labels for future insertions. Also, the proposed strategy can reduce the increment of label size in the case of frequent skewed insertions efficiently.

A Compact Bit String Accessibility Map for Secure XML Query Processing

One of the challenging issues related to specifying a fine-grained access control on the XML data is how to implement the accessibility map in a compact format with minimum affect on the XML query processing. In this paper, we propose a Compact Bit String Accessibility Map (CBSAM) to implement the accessibility map in a compact format. In order to achieve a secure and efficient XML query processing, the CBSAM is integrated with the region number labeling scheme. The experimental results illustrate that the CBSAM compresses the accessibility map with minimum affect on the XML query processing when the access locality among the XML nodes is high.

A Dynamic Compressed Accessibility Map for Secure XML Querying and Updating

By specifying a fine-grained access control on the XML data, an accessibility map is required to determine the accessibility of XML nodes for a specific subject (e.g. user or role) under a specific action (e.g. read or write). In the recent years, several research works have been done to reduce the overall storage cost of accessibility map with rapid determination of accessibility of XML nodes at runtime but there is no effort to implement the accessibility map in a compact format for dynamic environment where the accessibility of XML nodes can be updated frequently. In this paper, we propose a Dynamic Compressed Accessibility Map called DCAM to implement the accessibility map in a compact format which can be used in dynamic environment. Moreover, we suggest an efficient lookup method to determine the accessibility of XML nodes by labeling the authorization nodes in the DCAM with the dynamic XML labeling scheme. We also propose an efficient method to accelerate the process of checking the access authorizations for a set of XML nodes retrieved from the XML query processor when the access locality among the XML nodes in the XML tree is high. Besides, we define a set of constraints on the process of XML updating in order to maintain the DCAM in a compact format with minimum maintenance cost. The experimental results demonstrate that the DCAM is more efficient in both the space and time requirements for secure XML querying and updating.

An air indexing method for encrypted XML data broadcast in mobile wireless network

Recently, the use of XML for data broadcasting in mobile wireless networks has gained many attentions. One of the most essential requirements for such networks is data confidentiality. In order to secure XML data broadcast in mobile wireless network, mobile clients should obey a set of access authorizations specified on the original XML document. In such environments, mobile clients can only access authorized parts of encrypted XML stream based on their access authorizations. Several indexing methods have been proposed in order to have selective access to XML data over the XML stream. However, these indexing methods cannot be used for encrypted XML data. In this paper, we define a new unit structure for XML stream called SecNode which supports data confidentiality of XML data over the wireless broadcast channel. We also define two indexes for the SecNode structure called Min (NCS) and Min (NIS) to efficiently process XML queries over the encrypted XML stream.The experimental results demonstrate using two indexes Min (NCS) and Min (NIS) in the SecNode structure reduces the power consumption of mobile clients in processing XML queries over the encrypted XML stream.

Transferring Clinical Information between Heterogeneous Hospital Database Systems in P2P Networks

This paper proposes an approach for transferring clinical information between heterogeneous hospital database systems, using the XML standards and JXTA API in P2P networks. In this study, clinical information is transferred between two hospital database systems, which are semantically similar, but have different schema representations. The transferring is carried out through an intermediate XML data file as the bridge between these two data sources. The mapping is via two XML schemas, one from the source hospital to the intermediate data file, another is from the intermediate to the destination hospital. The approach is developed using Java programming language and JXTA API.