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The data grid (Belalem & Slimani, 2007; Yang, Fu, Huang, & Hsu, 2008; Yang, Tsai, Chen, & Hsu, 2007; Domenici, Donno, Pucciani, Stockinger, & Stockinger, 2004; Chang & Chang, 2006; Guy, Kunszt, Laure, Stockinger, & Stockinger, 2002; Mistarihi, & Yong, 2008) is a wide area computing infrastructure that provides huge storage capacity and great computing power to applications. Various applications (Bernholdt et al., 2005; Astakgov, Gupta, Santini, & Grethe, 2005) collect and analyze a large volume of shared data. These applications can always benefit from data grid of data management and data replication.
In the scenario of emergency and rescue operations (Plagemann, Munthe-Kaas, & Goebel; Plagemann et al., 2007), information (e.g. the list of available human resource and the list of destroyed buildings, etc.) sharing is the key to success or failure of the entire operation. However, efficient information sharing is difficult to achieve in such a scenario because there is no communication infrastructure at the disaster sites.
Usually the rescuers in the same site can use the Wi-Fi technique to set up a temporary wireless local area network (LAN) for the intra-site information sharing. On the other hand, the rescuers in different sites must generally use the GPRS, WCDMA, CDMA2000 techniques or even the satellite to form a wireless wide area network (WAN) for the inter-site information sharing. Although the signal strength could be strong enough in a wireless LAN, it is relatively very low in a wireless WAN. This situation infers that the network condition is relatively reliable in the intra-site environment but relatively unreliable in the inter-site environment. Moreover, the network partitioning problem may occur between two sites in the scenario of the emergency and rescue operation. Therefore, the replication technique (Chang & Chang, 2006; Deris, Abawajy, & Suzuri, 2004; Domenici, Donno, Pucciani, & Stockinger, 2006; Domenici, Donno, Pucciani, Stockinger, & Stockinger, 2004; Guessoum, Briot, Faci, & Marin, 2010; Guy, Kunszt, Laure, Stockinger, & Stockinger, 2002; Hara & Madria, 2009; Mistarihi & Yong, 2008; Saito & Shapiro, 2005; Sun & Xu, 2004; Tikar & Vadhiyar; Yang, Fu, Huang, & Hsu, 2008; Yang, Tsai, Chen, & Hsu, 2007) used in data grid should be adopted in emergency and rescue applications for improving the efficiency of the information sharing.
There are two advantages of using the replication technique. The first is reducing the data transfer time, and the other is providing the higher availability of shared data items. However, the consistency between all replicas of the data items is consequently an important issue in emergency and rescue applications.
The replication techniques (Chang & Chang, 2006; Guy et al., 2002) can be roughly classified into the optimistic and the pessimistic replication schemes. The optimistic replication scheme provides a more relax consistency guarantee, while the pessimistic replication scheme provides a stronger consistency guarantee.