# Enhanced Distributed Dynamic Skyline Query for Wireless Sensor Networks
###### Abstract  
Dynamic skyline query is one of the most popular and significant variants of skyline query in the field of multi-criteria decision-making. However, designing a distributed dynamic skyline query possesses greater challenge, especially for the distributed data centric storage within wireless sensor networks (WSNs). In this paper, a novel Enhanced Distributed Dynamic Skyline (EDDS) approach is proposed and implemented in Disk Based Data Centric Storage (DBDCS) architecture. DBDCS is an adaptation of magnetic disk storage platter consisting tracks and sectors. In DBDCS, the disc track and sector analogy is used to map data locations. A distance based indexing method is used for storing and querying multi-dimensional similar data. EDDS applies a threshold based hierarchical approach, which uses temporal correlation among sectors and sector segments to calculate a dynamic skyline. The efficiency and effectiveness of EDDS has been evaluated in terms of latency, energy consumption and accuracy through a simulation model developed in Castalia. wireless sensor networks; distributed data centric storage; skyline query; sector based distance routing; uniform distribution; lower bound distribution; and upper bound distribution Article  
[PERSON], 123,  
\(\left|x_{1}\left[m\right]-q\left[m\right]\right|<\left|x_{2}\left[m\right]-q\left[m \right]\right|\). In Figure 1b, points \(x_{1}\), \(x_{2}\) and \(x_{4}\) are the dynamic skyline points of \(q\). Each point \(x_{i}=\left(x_{i}[j],x_{i}[i]\right)\) is transformed to \(x_{i}^{\prime}=\left(x_{i}[j]-q[j],x_{i}[i]-q[i]\right)\). Skyline query is very useful in multi-preference analysis and decision making for environmental monitoring applications. For example, in a WSN deployed in a forest with each sensor node sensing temperature and wind speed, it is possible to build a fast and energy efficient forest fire detection method [11] by concentrating on places with high temperature or fast wind speed, or both. To illustrate the idea of dominance relations in this scenario, consider the readings in the two-dimensional attribute space shown in Figure 2 depicting a typical example of ranking objects by more than one criterion. Figure 2a lists nine records received from nine corresponding sensor nodes deployed in different places and their values. Figure 2b depicts the representation in a 2D space. Places P1, P2, P3, P5, and P6 are all dominated by other points so the skyline query returns the points that are not dominated by any other points. Consider the point P5 that is dominated by P7, as it has a higher wind speed than P5 though both have the same temperature. The skyline query only retrieves the dominant places in terms of higher temperature and wind speed. The skyline query will not exhibit any place with lower temperature and wind speed once it is dominated by a location with higher values. Therefore, the result set of the skyline query consists of {P4, P7, P8, P9}, which are indicators of dangerous places that need special attention. Figure 1: (**a**) TS and (**b**) DS (q, X). Figure 2: (**a**) Skyline of sensor readings, (**b**) Representation of sensor readings in 2D space [11]. Another example that demonstrates the usefulness of DS can be found when monitoring the air pollution in a region of interest. A high concentration of CO or SO\({}_{2}\), or both, can be a strong indication that the location is highly polluted. An environmental scientist can issue a dynamic skyline query for CO and SO\({}_{2}\) levels to monitor the air pollution surrounding a particular region of interest. DS query processing over moving objects is also very useful for numerous applications, such as location-aware computing, object tracking and monitoring, virtual environments, uncertain data stream, computer games, visualization, _etc._  
Although the skyline query approach has potential for use in WSN applications, it faces challenges because of high processing complexity and cost related with updating the results.