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, firewall, content filtering , etc., but with little success. Overall, Internet insecurity from three aspects , Internet deficiencies, lack of systematic safety standards and external unsafe environments. The three most important aspects is the first aspect of the Internet beginning of the design is intended to provide extensive connectivity , information sharing , interoperability , the focus is not safe , so it is a threat to network security , leading to the root cause of the network can not be trusted .

Mobile computing environment has the following characteristics [ 2,3 ] :
( A ) mobility and location correlation. Determine the characteristics of the mobile terminal in a wireless communication environment that it can move freely .
( 2 ) large-scale systems . In the user scale, the mobile environment is much more massive than the conventional network environment .
( 3 ) a variety of network environments. As the weather , temperature, and other conditions of the terrain , in different locations , the time is not the same as the networking conditions .
( 4 ) limited resources . The mobile device also by the storage capacity, network bandwidth, CPU processing capability limitations .
( 5 ) poor safety and reliability. Database system data privacy is high, in the face of collisions, magnetic interference such circumstances , personal data security is a serious threat.
( 6 ) of the frequent disconnection . Due to the power supply, wireless communication costs , network conditions, and other factors, mobile computers generally do not use continuous networking works, but even among active or passive , disconnected .
( 7 ) the asymmetry of the wireless network : general fixed server node has a powerful transmission device , the mobile node sends weak . Thus , the downlink and uplink communication bandwidth and cost of a larger difference .

Called database [ 7 ] refers to the long-term storage in a computer , organized , shared data collections. Data in the database data model by a certain organization , description, and storage , in particular smaller redundancy , the higher the data independence and ease of scalability , and for a variety of users. Database is the storage of data warehouses. The repository is simply a computer storage device , and the data is stored according to a certain format . history shows that from the database , the relevant data collection, data model organization formed in history appellation different database types . There are still accepted unified network database definition.

The so-called Web database , also known as network database . Can simply think , Web technology and database technology together to form a Web database technology . Resulting in a Web database . In essence , the network database is organized via computer network communications , storage, retrieval of the relevant data set [ 8 ] . The current relational database products such as Microsoft SQL Server, Oracle and other databases have network database functions, can be used as network database creation and development tools. Network database opens up a new era in the database . Mentioned below in my hotel management system that is used in WEB database . In general, the network database system has five major components: network operating systems, network database, network database management systems, network database administrators and network databas