HWP
From Just Solve the File Format Problem
HWP is Hancom Word's file format, and is based on Microsoft's OLE compound document format. A specification was released in 2010, but it is in Korean only.
References
- Questions on POLE library (and HancomWord support) Provides basic info on the format.
- [1] Further post in the thread, linking to the specification download page, and telling how to download and extract it properly.
- Hancom Word specification Make sure to read the post above.