This is the first time that industry has embraced a declarative representation that describes the service in a standard machine-readable form.
WSDL (Web Services Description Language) makes public the name of the service, the names of the operations, and most important the formats of the input and output messages for each operation, and the part names of each message component described as simple or complex XML types.
Public WSDL web services are registered at UDDI (Universal Discovery Description and Integration) nodes and in principle, an automated software program can discover and consume services at runtime by reading the WSDL.