Comparison between Web Services and other technologies

XMLHTTP and SOAP:
XML is the core technology of web serivces and the key to SOAP implementation. XMLHTTP is designed based on XML. In terms of implementation: XMLHTTP is browser-based. XML strings can be transmitted to the server as long as Internet Explorer is available, which is highly universal. However, browsers are not used for XMLHTTP. They are intended for public users. If you can use XML to perform various operations, it will inevitably affect users. For example, the browser corresponding to the previous version of msxml can access the XML document of the client (designed for XMLHTTP at the beginning), which means that the local file system can be accessed through XMLHTTP technology. Later, microsoft defined it as a vulnerability, and now it cannot work. Of course, you can also write client programs, but limited to Visual programs. They can call the APIs in msxml. However, the server can be asp, jsp, or servlet, all of which convert xml strings into xml document objects.
SOAP is a communication protocol in XML format. It includes the following: the SOAP envelope defines the agreement describing the message content, and implies the message processing method; protocol binding provides a general mechanism for transmitting SOAP envelopes through a lower-layer protocol. Encoding rules are conventions that map various application data types to tag-based XML representation methods; the RPC mechanism provides a method to indicate remote procedure calls and return values. It has no clear relationship with other protocols, and his province is an agreement. It can be bound to http. stmp, tcp, and other protocols. SOAP messages are XML documents and can contain attachments. They can generate SOAP messages based on W3C-defined APIs. Of course, microsoft's. net platform also supports SOAP. SOAP + HTTP is similar to XMLHTTP. When it provides better and more powerful implementation functions, it is scalable and universal in distributed collaborative communication, more importantly, it has become a key technology for Web Services and line communication.
SOAP and RMI, CORBA, COM
Both RMI and COM are implementation methods of distributed applications, which define the communication between components. Because they are only Communication Conventions between programs in a system (such as a series of programs written in java), and communication requires the support of specific platforms, in addition to the efficient communication within the system, it cannot be associated with procedures in other systems.
To solve this communication problem, CORBA designed a proxy request model (using the IDL language) to communicate with each other. However, it seems to be a repair and cannot solve the fundamental problem, the system becomes more and more complex, and the use of CORBA is only effective in restoring the value of the old system. Neither of them can pass through the firewall. SOAP + HTTP is a firewall-friendly protocol that can be passed through the firewall.
SOAP is a protocol unrelated to specific implementations. It transmits data in XML format based on XML format, making the system loose. In this way, the readability of XML is used in the application, and XML documents are parsed to implement the application, which greatly improves the system interoperability (communication with different systems ). In addition, the business logic of each unit in the system is clear, which is highly portable and reusable.