The TCP relational structure.
If the server offers both incoming and outgoing communication, as with
TCP/IP, then the relationship between the entities is bilateral, or mutual. If
the server is nothing more than a receiver and processor of information
without returning a confirmation of processes success or failure back to
the client post-process, as with UDP (User Datagram Protocol), then the
relationship is parasitic, or unilateral. In the case of XML Web services,
were virtually always dealing with bilateral relationships.
SOAP is not a first-tier or second-tier protocol (see Figure 1.1) because it
depends on a second-tier protocol for translation capabilities across the
InternetHTTP. In turn, the HTTP protocol depends on the TCP transport.
Instead, SOAP sits atop the other protocols. It uses its own standard speci-
fications supported by its own specific reserved words, designated num-
bers, and so forth. What makes SOAP really powerful and noteworthy is
that it supports language and platform interoperability through XML.
Another factor that makes the SOAP protocol remarkable is that the devel-
opers of the protocol brought structure and reusability to an age-old prac-
tice where standards were not always possible.
SOAP - Simple
All Others -
TCP Relational Structure
What Are Web Services?