WSDL, which stands for Web Service Description Language, is an XML-based standard used to describe the functionality of a web service. A WSDL document precisely defines how to communicate with the service. It specifies the service's location (endpoint), the operations (methods) it exposes through port types, and the format of the request and response messages, including data types and any required headers. This comprehensive, machine-readable description allows client applications to understand and interact with the web service without prior knowledge of its implementation details.

C. WSDL is exclusively based on XML (eXtensible Markup Language), not Object Notation like JSON.

D. The SOAP envelope is the wrapper for a SOAP message. WSDL is a separate document that describes the service; it does not wrap the message itself.

E. WSDL definitions are written only in XML. While web services can exchange JSON payloads, the WSDL standard itself does not use JSON for its structure.

1. W3C (World Wide Web Consortium). Web Services Description Language (WSDL) 1.1. W3C Note 15 March 2001.

Section 1.1, "What is WSDL?": "WSDL is an XML format for describing network services..." This directly supports that WSDL is written in XML (Options B, A) and not Object Notation or JSON (Options C, E).

Section 2.1, "WSDL Document Structure": This section details the core elements of a WSDL document, including , , and , which define the operations, request/response data, and service origin, confirming the details in Option A.

2. Oracle Help Center. Using the SOAP Adapter with Oracle Integration 3.

Chapter: "SOAP Adapter Capabilities": The documentation states, "The SOAP Adapter enables you to connect to SOAP-based web services. You configure the SOAP Adapter by providing the WSDL URL of the SOAP web service." This establishes the WSDL as the foundational XML document that defines the service for integration platforms like Oracle's.