WSDL (Web Services Description Language) is an XML-based, platform-independent meta language that can be used to describe the interface definitions of a Web service. WSDL mainly defines the functions of the Web service that are externally accessible, as well as the parameters and return values of these operations. WSDL mainly defines the functions of the Web service that are externally accessible, as well as the parameters and return values of these operations. Furthermore, it describes the communication format in which function calls are sent to Web services. The URL at which a Web service can be called is also specified.
A Web service must be published before the WSDL document describing it can be found, imported, and used. The publication contains detailed information on the location where the descriptive WSDL document was found.
Specifically, a WSDL document contains functional details about:
the interface
the access protocol and details about distribution
all information required to access the Web service in machine-readable format.
Web services are characterized by two groups of elements, that is, abstract and concrete definitions.
Concrete definitions, that is, implementation-specific information such as binding (defines the message format and protocol), port (specifies the address of a communication end point) and service (a collection of ports) are not currently used in the ARIS environment because modeling and Web services used in the models are intended to be platform-independent. Abstract definitions describe the interfaces, their operations and the message types and data types used, regardless of protocol or service.
The following elements represent the abstract definitions in WSDL:
Types
Collection of data type definitions that are used for the XSD type system (XML Schema Definition). The data types used are defined in an associated XML schema definition, the standard type system for describing data. Data types are the abstract definition of the structure of a section within an XML document and of a section of a WSDL description of a Web service in particular.
Message
Abstract, unidirectional definitions of the messages transferred. A message can contain the input or output of an operation. Messages consist of several logical parts, each of which is linked to a definition within a data type system.
Operation
Describes actions supported by the Web service. Messages are grouped in abstract operations.
PortType
Comprises a set of actions and represents an interface. Operations are grouped in abstract PortTypes. A WSDL description may contain multiple PortTypes.
PartnerLinkType
A PartnerLinkType indicates how two communication partners interact and what each party offers.
Binding
A binding defines the concrete protocol and data formats for operations and messages that are given by a particular PortType.
Service and port
A port specifies the address (usually a URI) for a binding. A service is a collection of related ports.