The Design And Implementation Of The Middleware-based Weather Information Subsystem

The rapid growth in military and civil aviation put lots of big-scale air traffic control (ATC) automation systems into use, which has placed more and more new and high requirements on these systems. With the development of ATC systems, the ATC automation software is becoming increasingly complex; the traditional developing methods can't meet the requirements. It is highly necessary that advanced developing methods be introduced into the development of ATC software. Taking the weather information system, a subsystem of ATC system, as a starting point, the paper intends to pave the way for the full-scale application of advanced technologies in development of ATC system by employing such advanced methods as UML-based analysis, middleware-based software architecture and design pattern-based implementation. The paper firstly gets the reader familiar with the framework of the ATC system and weather information subsystem, which makes it easier for the reader to proceed. Then, the paper analyses the subsystem under construction in detail using UML, which gives us a clear picture of the subsystem. The design and implementation of the subsystem is the important part of the paper. In this part, the paper first briefs the concept and types of middleware, and then the paper layered the subsystem into interface middleware, messaging middleware, network middleware and top layer-application layer. The paper discusses the design and implementation of the subsystem layer by layer. In the network middleware part, the paper put forward an UDP-based protocol, which enables the applications using the protocol to communicate without knowing the location of the counterpart. In the messaging middleware part, a messaging model was put forward. The paper discusses its working theory and modules, also give brief introduction to the data struct used in the messaging middleware. In the interface middleware part, the paper introduces the X-WINDOW and Motif briefly, and then it moves on to the encapsulation of the Motif. The practical use of the encapsulation of the Motif on multiple UNIX platforms such as Tru64, Sco Unixware proves the reliability and the platform-independent of the middleware. The paper also detailed the designs and implements the OCI interface of Oracle database, which facilitates the access to the database. The connection restore mechanism is discussed in the part. The Template Method design pattern is employed in the design and implementation of client side the application layer. The practise of the design pattern features the algorithm reused and therefor the maintenance of the code is easier-once the algorithm in base class is modified, the algorithm in devised class is modified too. Another improvement in this part is balancing the intelligence of the classes by moving the algorithm of error checking from the containing class to the contained interface elements. The operator overloading and type conversion function makes the code easier to write and maintain.