POI?

DDF?

HPSF?

HSSF?

SS?

I want to better understand the intent behind these namespaces.  Knowing what the abbreviations are should help.

I suggest you take a look at poi document. These names are copied from POI project.

POI - Poor Obfuscation Implementation

POIFS - Poor Obfuscation Implementation File System

DDF - Dreadful Drawing Format

HPSF - Horrible Property Set Format

HSSF - Horrible Spreadsheet Format

HWPF - Horrible Word Processor Format

HSLF - Horrible Slide Layout Format

HDGF - Horrible Diagram Format

HPBF - Horrible Publisher Format

HSMF - Horrible Stupid Message Format

SS - Spreadsheet

XSSF - XML Spreadsheet Format

Ref: http://en.wikipedia.org/wiki/Apache_POI