D3L (Data Definition Description Language) is an XML-based message description language that describes the structure that an application's native, non-XML format message (known also as its native view) must follow to communicate. Currently used in Oracle Application Server InterConnect, D3L message description language is used to interact through several transport adapters, including FTP, HTTP(S), MQ Series, and SMTP.
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D3L Wikipedia(Text) CC BY-SA