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ECLIPSE WEB TOOLS PLATFORM developing java web applications PHẦN 7

các công nghệ như CORBA, Java RMI, DCOM thất bại để đạt được lực kéo đáng kể trên mạng Internet. Khi XML xuất hiện, Microsoft đã đề xuất rằng nó có thể được sử dụng như là một cách kiến trúc trung lập để tuần tự hóa các đồ thị của các đối tượng. SOAP đã được đề xuất là người vận chuyển cho các đối tượng đồ thị tuần tự và thuật toán tuần tự được mệnh danh là mã hóa SOAP. . | 424 CHAPTER 10 Web Services technologies such as CORBA Java RMI and DCOM failed to gain significant traction on the Internet. When XML emerged Microsoft proposed that it could be used as an architecturally neutral way to serialize graphs of objects. SOAP was proposed as the carrier for these serialized object graphs and the serialization algorithm was dubbed SOAP encoding. The fact that XML was used as the serialization syntax was incidental. To use SOAP encoding you had to have matching client and service implementations that understood the SOAP encoding algorithm. The client and the server were assumed to both be implemented in conventional object-oriented programming languages. The flaw in this approach is that exchanging objects is really not what the Web is all about. The Web is highly heterogeneous and there are many types of clients and ways of processing XML. For example XML can be processed using DOM SAX StAX XPath XSLT and XQuery to name a few. In fact one of the design principles behind XML is that it should be easily processable by a variety of applications. SOAP encoding clearly violates that principle. A better approach to the design of Web service interfaces is to view Web service operations as document exchanges. After all business in the real world is transacted by the exchange of documents. For example I fill out a driver s license application form and the motor vehicle department sends me my driver s license. I do not remotely invoke the driver s license procedure or send the motor vehicle department a serialized driver s license application form object graph. Documents are very natural and XML is an excellent way to represent them in information systems. XML Schema is the W3C standard type system for XML documents. But XML is really just a representation of a document albeit a very convenient one for many purposes. In general there may be other useful representations of documents. For example if I just want to display the document to a human .