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being based on XML, thus making WSDL suitable to describe almost
any type of service.
• WSDL provides a method of specifying a communication protocol
for invoking a service. Therefore, a service is free to choose any pro-
tocol it can conveniently implement.
• WSDL also provides a way to specify a message format for commu-
nicating with a given service. Therefore, a service is free to choose
any convenient message format. An example of a message format is
S OA P.
• WSDL also provides wide latitude for the service provider to specify
the type of service operations they offer. In general, four different
types of service operations can be specified, including synchronous
operations and asynchronous operations.
• Finally, WSDL has a method for specifying a service endpoint.
A service endpoint is the network address at which the service is
available for invocation.
WSDL is used to describe Web Services, including their interfaces, meth-
ods, and parameters. WSDL characterizes the interface, which consists of
two parts:
1. An abstract interface description containing the supported opera-
tions, the operation parameters, and their types
2. A binding and implementation description containing a binding of
the abstract description to a concrete transport protocol, message
format, and network address
The WSDL description of a service called StockQuoteService that provides a
single operation named GetLastTradePrice is depicted in Listing 8.2.
Listing 8.2 WSDL for the GetLastTradePrice service
<?xml version = "1.0"?>
<definitions name = "StockQuote"
targetNamespace = "http://myCompany.com/
stockquote.wsdl"
xmlns:tns = "http://myCompany.com/stockquote.
wsdl"
xmlns:soap = "http://schemas.xmlsoap.org/wsdl/
soap/"
xmlns:xsd = "http://www.w3.org/2001/XMLSchema"
xmlns = "http://schemas.xmlsoap.org/wsdl/">
[Abstract data type definitions]
<message name = "GetLastTradePrice">
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