SOAP is an abbreviation for Simple Object Access Protocol. This is a computer protocol used for communication between different components or servers. SOAP is supported by many companies and organizations including Sun, IBM, Novell, Microsoft, Oracle, Apache Software Foundation and the former BEA Systems (now Oracle). SOAP is a protocol that sends XML messages, usually over HTTP, but also over SMTP, HTTPS or FTP.
WSDL stands for Web Services Description Language. WSDL is part of SOAP. This defines the standard elements of a web service used. A WSDL defines the structure and required format of the data types within the Web service messages. At Buckaroo, the WSDL is recorded for all services as Single WSDL. A SOAP WSDL is also available.
XSD stands for XML Schema Definition and describes the relationship between the different elements of an XML object. This can be for the entire service or for a part. In this way, the definitions of the interfaces are laid down in a standard.