The abstract says "We have used IPGs to specify a number of file formats including ZIP, ELF, GIF, PE, and part of PDF". Sounds to me like they threw PDF in ther

The abstract says "We have used IPGs to specify a number of file formats including ZIP, ELF, GIF, PE, and part of PDF". Sounds to me like they threw PDF in there to test the limits of the technique _after_ using it on a bunch of other unrelated formats. In fact, the authors state "PDF is picked because it is the most complicated format to our knowledge, which requires some unusual parser behaviors. We did not implement a full PDF parser due to its complexity, but a functional subset to show how IPGs can support some interesting features (...) PDF is a more complicated format. Our IPG grammar for PDF does not support full PDF parsing but focuses on how some interesting features in PDF are supported. As a result, the parser generated from our IPG PDF grammar can parse simple PDF files"