A Study On Reflective Hydro-Database Access Middleware

Water resources data centre is one of the most important infrastructures for hydro-information development and utilization, especially its sharing by many departments. Water resources data access middleware is capable of integrating various heterogeneous data sources and providing transparent and efficient data access. How to research and develop novel data access middleware, which can adapt to open and dynamic Internet environment, has become a hot research topic nowadays. Reflection enables a program to access, monitor and modify its own state or behavior, which is firstly put forward by B.C. Smith in 1982 at M.I.T. This dissertation makes an intensive study on reflective middleware with both respect to theoretical aspect and application concern.After reviewing the existing reflection theory and various models, this dissertation proposes a formal specification model for reflective middleware, which is based on timed automata. By using timed automata to specify meta level, base level and their causal connection, our model is able to describe the reflection process more clearly, compared with other models.This dissertation proposes a reflective domain middleware framework, with the quality of service (QoS) reconfiguration mechanism and the creation of reflective meta-level. Our framework can adapt for the dynamic resource environment and ensure dynamic QoS. Furthermore, a concrete model, Reflected Middleware Model (ReMM) is implemented based on J2EE architecture, which can conduct re-configuration according to the dynamic variation of QoS parameters.To obtain an effective and efficient data access middleware, this dissertation also proposes a new cost function for distributed query optimization under code shipping architecture, which takes the dynamic network environment and operation costs into considerations at the same time. At last, this dissertation depicts the practical solutions for a reflective hydro-database middleware system based on ReMM, which can be put into use in provincial government.The integration of the reflective technology and the query optimization in the database middleware has seldom been studied previously. The work in this dissertation shows a good direction of this research. Moreover, because the...