It's possible you might be referring to a specific, less common or internal language used within a particular organization or system.
To understand what you're looking for, please provide more context:
* Where did you encounter this term? (e.g., a document, presentation, software interface)
* What is the general context? (e.g., data storage, database management, cloud computing)
* What is the purpose of this language? (e.g., defining storage structures, configuring storage devices, managing data access)
With more information, I can help you understand what SDL means in your specific context.