Service/Service: The service can be thought of as a container for a set of system functions that have been exposed to the web based protocols.
Port/Endpoint: The port does nothing more than defining the address or connection point to a web service. It is typically represented by a simple http url string.
Binding/Binding: Specifies the interface, defines the SOAP binding style (RPC/Document) and transport (SOAP Protocol). The binding section also defines the operations.
PortType/Interface: The <portType> element, which has been renamed to <interface> in WSDL 2.0, defines a web service, the operations that can be performed, and the messages that are used to perform the operation.
Operation/Operation: Each operation can be compared to a method or function call in a traditional programming language. Here the SOAP actions are defined and the way the message is encoded, for example, "literal."
Message/N.A.: Typically, a message corresponds to an operation. The message contains the information needed to perform the operation. Each message consists of one or more logical parts. Each part is associated with a message-typing attribute. The message name attribute provides a unique name among all messages. The part name attribute provides a unique name among all the parts of the enclosing message. Parts are a description of the logical content of a message. In RPC binding, a binding may reference the name of a part in order to specify binding-specific information about the part. A part may represent a parameter in the message; the bindings define the actual meaning of the part. Messages were removed in WSDL 2.0, in which XML schema types for defining bodies of inputs, outputs and faults are referred to simply and directly.
Types/Types: The purpose of the types in WSDL is to describe the data. XML Schema is used (inline or referenced) for this purpose.
WSDL 1.0 (Sept. 2000) has been developed by IBM, Microsoft and Ariba to describe Web Services for their SOAP toolkit. They built this by combining two service description languages: NASSL (Network Application Service Specification Language) from IBM and SDL (Service Description Language) from Microsoft.
WSDL 1.1, published in March 2001, is the formalization of WSDL 1.0. No major changes were introduced between 1.0 and 1.1.
WSDL 1.2 (June 2003) is still a working draft at W3C. According to W3C: WSDL 1.2 is easier and more flexible for developers than the previous version. WSDL 1.2 attempts to remove non-interoperable features and also defined the better HTTP 1.1 binding. WSDL 1.2 was not supported by most of the SOAP servers/vendors.
WSDL 2.0 became a W3C recommendation on June 2007. WSDL 1.2 was renamed to WSDL 2.0 because it has substantial differences from WSDL 1.1. The changes are:
* Adding further semantics to the description language
* Removal of message constructs
* No support for operator overloading
* PortTypes renamed to interfaces
* Ports renamed to endpoints.
