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Software defined network (SDN) is a new modern network technology which decouples control plane and data plane to simplify network management. The separation of control plane from data plane arises the control placement problem (CPP) in these networks. The main questions in the CPP are (1) how many controllers are required to be used in such networks and (2) where these controllers should be placed. To achieve an efficient solution for such problem in SDN, we define the CPP as a multi-objective combinational optimization problem in this paper and solve the CPP by applying the antlion optimization algorithm on it. We consider three metrics for the CPP: (a) Inter-controllers latency, (b) switch to controller latency, and (c) multiple disjoint connectivity paths between switches and controllers. We evaluate our proposed solution by performing several experiments using different real network topologies. Experimental results show that our proposed solution provides better performance compared to the existing solutions.

A data stream exhibits as a massive unbounded sequence of data elements continuously generated at a high rate. Stream databases raise new challenges for query processing due to both the streaming nature of data which constantly changes over time and the wider range of queries submitted by the user when compared with the traditional databases. In this paper, we propose a system architecture which includes components for both distributed indexing of streaming data and distributed processing of range queries over streaming data. By exploiting the proposed system architecture, the process of indexing of streaming data and the process of querying over streaming data can be done in a distributed fashion. We also design a distributed B + Tree indexing method using the map-reduce programming model of the Apache Spark framework which creates small B + Tree indexes on the machines of a Spark cluster instead of using a large and centralized B + Tree index structure. Moreover, we propose a distributed range search algorithm to process range queries in distributed and parallel form using the set of small B + Tree indexes. By performing several experiments, we demonstrate that our proposed distributed B + Tree indexing method is scalable and efficient compared to the existing indexing methods and therefore, it can be used for applications involving data streams with a large volume of data elements and a large number of range queries.

Broadcasting is one of the basic ways to access XML data via mobile wireless networks. In these networks, XML data are disseminated over a wireless broadcast channel and mobile clients can connect to this channel via portable devices and receive the XML data they need. To date, various indexing methods have been proposed to broadcast the XML data over mobile wireless broadcast networks, each of which attempts to reduce the latency and energy consumption of mobile devices in processing the different types of XML queries. Most of the proposed indexing methods use only a single wireless broadcast channel for XML data dissemination. Due to the sequential data access over a wireless broadcast channel, the access time to retrieve the desired XML data over a broadcast channel is longer if the length of generated XML data stream is large. This paper proposes two new XML data placement schemes to disseminate the XML data over multiple wireless broadcast channels by partitioning the XML data stream into several partitions and placing them into multiple wireless broadcast channels. The goal of both of which is a further reduction of the access time during the process of XML querying over the broadcast channels. According to the experimental results, the proposed XML data placement schemes have achieved the goal of further reducing the access time, especially when the size of XML document to be disseminated is large.

Todays, XML as a de facto standard is used to broadcast data over mobile wireless networks. In these networks, mobile clients send their XML queries over a wireless broadcast channel and recieve their desired XML data from the channel. However, downloading the whole XML data by a mobile device is a challenge since the mobile devices used by clients are small battery powered devices with limited resources. To meet this challenge, the XML data should be indexed in such a way that the desired XML data can be found easily and only such data can be downloaded instead of the whole XML data by the mobile clients. Several indexing methods are proposed to selectively access the XML data over an XML stream. However, the existing indexing methods cause an increase in the size of XML stream by including some extra information over the XML stream. In this paper, a new XML stream structure is proposed to disseminate the XML data over a broadcast channel by grouping and summarizing the structural information of XML nodes. By summarizing such information, the size of XML stream can be reduced and therefore, the latency of retrieving the desired XML data over a wirless broadcast channel can be reduced. The proposed XML stream structure also contains indexes in order to skip from the irrelevant parts over the XML stream. It therefore can reduce the energy consumption of mobile devices in downloading the results of XML queries. In addition, our proposed XML stream structure can process different types of XML queries and experimental results showed that it improves the performace of XML query processing over the XML data stream compared to the existing research works in terms of access and tuning times.

In mobile wireless broadcast networks, XML data is encrypted before it is sent over the broadcast channel in order to ensure the confidentiality of XML data. In these networks, mobile clients must not have access to all the XML data; rather they should have access to some parts of the XML data that are relevant to them and to which they are authorized to have access. In this paper, a new encrypted XML data stream structure is proposed which supports the confidentiality of XML data over the broadcast channel. In our proposed stream structure, the size of encrypted XML data stream is reduced by grouping the paths, XML nodes, texts, and attributes together. The proposed structure includes several indexes to skip from irrelevant data over the broadcast channel. The experimental results demonstrate that the use of our proposed stream structure efficiently disseminates XML data in mobile wireless broadcast networks in a secure manner and the indexes in our proposed stream structure improve the performance of XML query processing over the encrypted XML data stream.

A new structure for streaming the XML data is proposed which guarantees confidentiality of the XML data over the wireless stream.An access mechanism is proposed to efficiently process XML queries over the encrypted XML stream. 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 networks, 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 structure for XML stream which supports data confidentiality of XML data over the wireless broadcast channel. We also define an access mechanism for our proposed structure to efficiently process XML queries over the encrypted XML stream. The experimental results demonstrate that the use of our proposed structure and access mechanism for XML data broadcast efficiently disseminates XML data in mobile wireless networks.

Security in wearable sensor networks and telecare medical information systems (TMIS) has turned to an issue of scholarly interest in recent years. Adequate security to agree on a temporary session key is essential for establishing a secure connection on various layers of the protocol stack in the Internet of Things (IoT) environments. Recently, Gupta et al. proposed a lightweight authentication and key agreement scheme for wearable sensing devices. Our analysis of Gupta et al.’s scheme revealed that it is insecure against privileged-insider attack, compromise sensing device, and desynchronization attacks in wearable sensor registration and login and authentication phases. In this paper, a Scalable Healthcare Authentication Protocol with Attack-Resilience and Anonymous Key-agreement, SHAPARAK, is proposed to overcome security flaws of existing schemes. The proposed protocol offers more scalability as it uses a public channel in the process of registration of each wearable sensing device. It also contains the password and biometrics changing phase without involvement of the trusted server. The security analysis of the proposed scheme is evaluated using the GNY logic, AVISPA tool, random oracle model, and informal security analysis. It is also shown that the proposed protocol is cost-efficient in terms of computation and communication overheads, compared to the existing schemes.

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.

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.

The concept of workflow is used for modeling many of the data-intensive scientific applications executed on data grids. A Workflow is a series of interdependent tasks during which data is processed by different tasks. Scheduling the workflows in the grids is the process of assigning tasks to appropriate resources with the aim of achieving goals such as reducing workflow completion time while considering the data dependencies between the tasks. Data access time, processing time, and waiting time together constitute task completion time in the grids. Workflow scheduling aims to optimize these parameters in such a way that the workflow completion time decreases, and the system efficiency improves. In this paper, a scheduling model based on multi-objective optimization is proposed for scheduling data-intensive workflows in data grids. The scheduling model aims to optimize data communication cost, waiting time, and tasks processing time while considering data dependencies between the tasks. The model defines the data communication cost in terms of data transfer time in various communications between nodes (intra-and inter-cluster communications). This study uses four different Multi-Objective Evolutionary Algorithms (MOEAs) as well as Random Search (RS) algorithm to implement the proposed scheduling model. Convenient coding mechanisms for representing chromosomes, compatible crossover and mutation operators were also designed. Simulation results of the proposed scheduling model using different optimization algorithms are presented. The results are then assessed and compared based on different quality indicators.

In order to facilitate the XML query processing, several labeling schemes have been proposed to directly determine the structural relationships between two arbitrary XML nodes without accessing the original XML documents. However, the existing XML labeling schemes have to re-label the pre-existing nodes or re-calculate the label values when a new node is inserted into the XML document during an update process. In this paper, we devise a novel encoding scheme based on the fractional number to encode the labels of the XML nodes. Moreover, we propose a mapping method to convert our proposed fractional number based encoding scheme to bit string based encoding scheme with the intention to minimize the label size and save the storage space. By applying our proposed bit string encoding scheme to the range-based labeling scheme and the prefix labeling scheme, the process of re-labeling the pre-existing nodes can be avoided when nodes are inserted as leaf nodes and sibling nodes without affecting the order of XML nodes. In addition, we propose an algorithm to control the increment of label size when new nodes are inserted frequently at a fix place of an XML tree. Experimental results show that our proposed bit string encoding scheme provides efficient support to the process of XML updating without sacrificing the query performance when it is applied to the range-based labeling schemes.

Problem statement: In order to facilitate XML query processing, labeling schemes are used to determine the structural relationships between XML nodes. However, labeling schemes have to reliable the existing nodes or recalculate the label values when a new node is inserted into the XML document during XML update process. EXEL as a labeling scheme is able to remove relabeling for existing nodes during XML update process. Also, it is able to compute the structural relationship between nodes effectively. However, for the case of skewed insertions where nodes are always inserted at a fixed place, the label size of EXEL scheme increases very fast. Approach: This study discussed how to control the increment of label size for the EXEL scheme. In addition, EXEL does not consider the process of deleting labels. We also study how to reuse the deleted labels for future label insertions. Results: We proposed an algorithm which is able to control the label size increment. Conclusion: It required less storage size to store the inserted binary bit string and thus can improve query performance.

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.

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.

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.