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> In the past, developers had to write code and learn to accept > any file > PDF Acrobat would They still do. Developers should never, ever use this approach in writing PDFs, only reading them. > > The problem is now the spec tightens No, the spec does not change. Acrobat does more checks. The different is important in understanding where the fault lies. It doesn't make it any less annoying. > There's also the problem of archives full of old PDF's > that are > still used, but now invalid - should Acrobat 6.0 make me change them > just because the spec used to be loose? The problem is that files slip through not because of a conscious decision but because the program simply fails to check. From time to time, people are likely to reimplement parts of their code. In Acrobat 5, the trigger for this was transparency, which required a more rigorous separation of objects if you were to be able to display thjem correctly. At that time, the programmer returns to the specification, rather than trying to allow all (and only) the errors it accepted before. I have seen one file that is rejected with Acrobat 6.0. The xref table looked like this .... 0000000001 00000 n -000000001 00000 n .... How did any programmer (at IBM, I think this one was) ever think that was a valid PDF to release on the public? > How do we hit a changing spec > without a way to detect the changes? You don't. It isn't changing. You just follow it closely. > Last time I checked no > documentation was available on what a new release of Acrobat would no > longer support as far as PDF is concerned. Because the errors accepted are almost entirely side effects, I don't think anyone would know until this kind of thing starts happening. It would be rather nice if Adobe's policy was to always accept faulty PDFs if some earlier release did, and that they would consider this a bug to fix. But this isn't their policy. As developers, faced with living in the shadow of PDF, we just have to evolve strategies for dealing with it... Aandi To change your subscription: http://www.pdfzone.com/discussions/lists-pdfdev.html
