PDF/A-3 makes only a single, fairly monumental change. In the PDF/A-2 specification users were allowed to embed files, but only PDF/A files. PDF/A-3 now allows the embedding of any arbitrary file format, including XML, CSV, CAD, images and any others.
At first glance this sounds like a gigantic betrayal of everything that the format has stood for. Why define a subset of PDF attributes to ensure the long-term comprehension of the file if you’re going to turn around and allow the kitchen sink to be embedded within it? (You can follow some of the original discussion of this change here.) http://blogs.loc.gov/digitalpreservation/2012/11/all-in-embedded-files-in-pdfa/?loclr=blogsig This is very bad news for digital preservation because it is now possible to "hide" proprietary digital inside the PDF/A digital container. What will future researchers think when they stumble upon these "hidden" closed formats that they will not be able to use? What were they thinking??
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