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Chapter 6 The Cloud
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Figure 6-15a
Example XML Document

{
"firstName": "Kelly",
"lastName": "Summers",
"dob": "12/28/1985",
"address":{
"streetAddress": "309 Elm Avenue",
"city": "San Diego",
"state": "CA",
"postalCode": "98225"
},
"phoneNumber": [
{
"type": "home",
"number": "685 555 1234"
},
{
"type": "cell",
"number": "685 555 5678"
}
Figure 6-15b ]
Example JSON Document }

Service authors (computer programmers) create WSDL documents to describe the services
they provide and the inputs and outputs required. These WSDL documents are seldom read by
humans. Instead, developer tools like Microsoft Visual Studio read the WSDL to configure the
programming environment for programmers who write code to access that service.
As shown in Figure 6-14, SOAP, which is not an acronym though it looks like one, is a
protocol that sits on top of http and the lower-level Internet protocols. Sits on top of means that it
uses http to send and receive SOAP messages. (SOAP can also use smtp.) Programs that use Web
services issue SOAP messages to request services; the Web service uses SOAP messages to return
responses to service requests.
Finally, XML and JSON are ways of marking up documents so that both the service requestor
and the service provider know what data they’re processing.Figure 6-15 shows a simple example
of both. As you can see, XML documents contain as much metadata as they do application data.
These metadata are used to ensure that the document is complete and properly formatted. XML
is used when relatively few messages are being transmitted and when ensuring a complete and
correct document is crucial. Both WSDLs and SOAP messages are coded in XML.
As its name indicates, JSON uses the notation for JavaScript objects to format data. It has
much less metadata and is preferred for the transmission of voluminous application data. Web
servers use JSON as their primary way of sending application data to browsers.