In this paper, we define a new type of coverage problem named target-barrier coverage problem in wireless sensor networks. A target-barrier is a continuous circular barrier formed around the target. The target-barrier has a dboundconstraint that is set depending on applications and needs, where dboundis the minimum distance of the constructed barrier from the target. Target-barrier coverage is very suited for application in defense surveillance, including detection of intrusion from outside and prevention of barrier breaching from inside. For instance, in a jail scenario, sensors can be deployed to enclose a jail with the constraint of dboundto detect the escape of prisoners or unauthorized entry into the jail for rescuing prisoners. We focus on how to minimize the number of members required to construct target-barriers in a distributed manner while satisfying the dboundconstraint and minimizing the amount of message exchange required. In performance evaluation, we compare our solution with the solution of related work and the Brute-Force algorithm which can find the minimum number of target-barrier members required. Our experimental results show that the proposed algorithm delivers satisfactory results in terms of the number of target-barrier members required and the amount of message exchange required.

Model-driven engineering is the generation of software artefacts from abstract models. This is achieved through transformations that encode domain knowledge and implementation strategies. The same transformations can be used to produce quite different systems, or to produce successive versions of the same system. A model-driven approach can thus reduce the cost of development. It can also reduce the cost of verification: if the transformations are shown or assumed to be correct, each new system or version can be verified in terms of its model, rather than its implementation. This paper introduces an approach to model-driven engineering that is particularly suited to the development of critical information systems. The language of the models, and the language of the transformations, are amenable to formal analysis. The transformation strategy, and the associated development methodology, are designed to preserve systems integrity and availability.

Current heterogeneous wireless networks often overlap because of their complementary characteristics and the large deployment of various wireless access technologies. Mobile devices, which are equipped with multiple wireless interfaces, called multiple radio access technologies (multi-RATs) mobile stations (MSs), are also becoming increasingly popular. Therefore, common radio resource management (CRRM) has been proposed to coordinate heterogeneous radio resource allocations and improve the resource utilization of heterogeneous wireless networks. However, CRRM is an NP-hard problem, and low-complexity approaches for dynamic resource management are in high demand. In this paper, the resource request and allocation between multi-RAT MSs and heterogeneous wireless networks are modeled as a directed graph. Thus, the problem of searching for feasible radio resource allocations is simplified to finding trees in a directed graph. Based on the proposed model, a heuristic scheme can be used to find a feasible solution efficiently, and dynamically adjust the workload of heterogeneous BSs to accommodate new requests. Experimental results demonstrate that the heuristic scheme can reduce the request reject rate by 10%-55% compared with conventional approaches.

We study the problems of race condition and process synchronization, commonly found in concurrent programming, in the context of information systems. These systems hold large quantities of business data constrained by complex structural and semantic rules. We assume that operations are equipped with guards against any violation of the data integrity, and that workflows (i.e. complex patterns of interactions) operate upon a shared, sequential data component. Updates via parallel workflows, through interleaving their operations, may lead to a state where the integrity is maintained but a goal property is not satisfied. Given workflows to be run in parallel, we calculate a precondition for establishing a state property upon their termination. Our calculation is efficient, using dynamic programming, and is based on the weakest precondition semantics of individual operations, we prove its correctness via a structural induction on the data structure: a 2-dimensional matrix.

In the process of specifying update operations of an information system, it is critical to ensure that the resulting design is consistent with the developers' understanding about the requirements, before it is adapted to a chosen platform of implementation. We present a formal approach to testing behavioral specifications that characterise the intended effects on the state as two-state, first-order predicates. By supplying use-case scenarios that are of interest, the developers are able to examine the test results, decide if the model under test is consistent, and revise the source specifications if necessary. To facilitate an iterative process of this, in this paper we develop a list of equivalence and refinement (rewriting) laws of predicates that are targeted at information system states. Our development is built upon the formal semantics and logical properties of a formal language of substitutions that serves as an abstract implementation language for these predicates.

Many information systems hold data of considerable value, and are subject to complex constraints and business rules. In these systems, update operations are often carefully described, to the extent that it is possible to derive a formal specification of their applicability and effect. Where an update is performed by means of a workflow, as a combination of operations, then it may be advantageous to calculate properties of that workflow from the specifications of the operations involved. This paper introduces a formal notation for the description and analysis of workflows, similar to the well-known languages of guarded commands or generalised substitutions. This notation is given a behavioural semantics corresponding to a sequential, transformational view of the information system. This semantics can then be used to determine the suitability of proposed guards-constraints upon the enactment of workflows-and to establish whether one workflow will interfere with the progress of another.

In model-driven development, requirements are captured as a specification model, from which a conforming implementation is automatically generated. Model consistency, with respect to requirements, is a primary concern. If the various structural and integrity constraints are inconsistent, then either the model will admit no implementation, or the implementation produced will not behave according to the intended requirements. We present an approach, based upon data-flow testing, to helping developers inspect their models for inconsistency. System models contain classes, attributes, invariants, and methods specified as first-order predicates. We identify for every attribute its intra-method usages. We construct accordingly call sequences demonstrating its inter-method usages. We derive from each call sequence a Boolean constraint, as a test case, ensuring both the execution of the corresponding inter-method usage and the maintenance of invariants. Developers may examine this test suite and compare against their original understandings about the requirements.