Computable Document Format
From Just Solve the File Format Problem
Computable Document Format (CDF) is a dynamic document format associated with the Mathematica mathematics software. It is a text format, apparently based on Wolfram Language (Mathematica format).
CDF is publicly documented, but it is pretty much impossible to properly render it without using components of the proprietary Mathematica software.
Specifications
- Wolfram Language & System Documentation Center - Allegedly, CDF is documented here.