An article by Yvonne Friese does a good job of explaining the limitations of JHOVE in validating PDF/A. At the time that I wrote JHOVE, I wasn’t aware how few people had managed to write a PDF validator independent of Adobe’s code base; if I’d known, I might have been more intimidated. It’s a complex job, and adding PDF/A validation as an afterthought added to the problems. JHOVE validates only the file structure, not the content streams, so it can miss errors that make a file unusable. Finally, I’ve never updated JHOVE to PDF 1.7, so it doesn’t address PDF/A-2 or 3.
I do find the article flattering; it’s nice to know that even after all these years, “many memory institutions use JHOVE’s PDF module on a daily basis for digital long term archiving.” The Open Preservation Foundation is picking up JHOVE, and perhaps it will provide some badly needed updates.