Thursday, December 6, 2007

Bit rot antidote

PDF 1.7 is now a Draft International Standard, soon to become ISO 32000.

In my October 30 post on Photo permanence and durability I had written about the problem of bit rot. For documents, since 1993 the best antidote for bit rot has been PDF (Portable Document Format). In fact, since then I always keep a copy of my documents in its original format and in PDF. Most of my tutorial materials are created in FrameMaker, but since Adobe abandoned it on the Mac platform, I often end up making small changes directly in the PDF file, which I can edit in Illustrator or in PitStop, depending on the edit's nature.

Now PDF 1.7 has become an even more potent antidote to bit rot, because the ISO has promoted it to a Draft International Standard. To learn more about this, read Jim King's PDF blog entry of December 4 with title ISO Ballot for PDF 1.7 Passed!.

Above I wrote explicitly about documents, not about pictures. If you put your pictures in a PDF file you will always be able to read them, but note that PDF is a structured file format, not a file format for images. Therefore, inside a PDF file, the image will be encoded for example in GIF, JPEG or JPEG-2000. These encodings are also ISO standards, so there will always be decoders for them. However, JPEG does not specify a file format, so wrapping JPEG images in a PDF file is better against bit rot. This is not an issue for JPEG-2000, which specifies also file formats.