[free-sklyarov] Using PDF

[Nick Moffitt]

So, here's a very nice writeup on the issues surrounding PDF.  I for
one use xpdf, which does not come from Adobe, is Free Software, and
which does not implement copy restriction methods.

I found it amusing that people on here were apologising for putting up
PDFs, even though they were alongside *extremely* proprietary Word
"doc" files.  

There are issues surrounding PDF 1.4, which is best left to someone
like Raph Levien to explain.  Most of the patents surround the color
management routines, and are based on Heavy Math.

----- Forwarded message from Rick Moen -----

As I mentioned, I'm mostly keeping my mouth shut and concentrating on 
learning, in an area where I'm woefully lacking.[1]  Apologies for length:
Feel welcome to skip this if you don't have time.

> PDF would work except that it, too, is proprietary -- and we are *not*
> happy with ADOBE this week.

The symbolism would indeed be unfortunate.  The question of what makes a
format proprietary is an interesting one:


My understanding is that Adobe pretty much cut itself off, early on, from
legal bullying[2] against PDF-compatible software, and hasn't done the
Microsoft trick of keeping it be a moving target and poorly documented.

PDF format (v. 1.3 = current) is well-documented, and (I'm pretty sure that)
Adobe long ago committed to make it interoperable with anyone else's
implementations.  In its PDF technical reference[3], Adobe says:

  ...[Adobe] owns the copyright for the particular data structures and
  operators and the written specification constituting the interchange
  format called the Portable Document Format.  Thus, these elements of
  the Portable Document Format may not be copied without Adobe's permission.

  Adobe will enforce its copyright.  Adobe's intention is to maintain the
  integrity of the Portable Document Format standard.  This enables the
  publicto distinguish between the Portable Document Format and other
  interchange formats for electronic documents.  However, Adobe desires
  to promote the use of the Portable Document Format for information 
  interchange among diverse products and application.  Accordingly, 
  Adobe gives copyright permission to anyone to:

  o  Prepare files whose content conforms to the Portable Document Format.
  o  Write drivers and applications that produce output represented in the
     Portable Document Format.
  o  Write software that accepts input in the form of the Portable Document
     Format and displays, prints, or otherwise interprets the contents.
  o  Copy Adobe's copyrighted list of data structures and operators, as
     well as the example code and PostScript language function definitions
     in the written specification, to the extent necessary to use the 
     Portable Document Format for the purposes above.

  The only condition of such copyright permission is that anyone who uses
  the copyrighted list of data structures and operators in this way must
  include an appropriate copyright notice.  This limited right [...]
  nor does it include the right to use any Adobe patents (except as may be
  permitted by an official Adobe Patent Clarification Notice).

The copyright song-and-dance is big of them, but is really a lot of hooey,
from the point of view of open-source developers.  The above means only
"If you're a really lazy coder, and can't figure out how to write your 
own compatible data structures, you can copy ours and not have to worry 
about being sued, as long as you credit us."

Patents, on the other hand, are a bigger issue, but this is where Adobe 
says something meaningful.

  Patent Clarification Notice

  Adobe has a number of patents. [...]  Adobe desires to promote the use of
  PDF for information interchange among diverse products and applications. 

  Accordingly, the following patents are licensed on a royalty-free,
  non-exclusive basis for the term of each patent and for the sole purpose
  of developing software that produces, consumes, and interprets PDF files
  that are compliant with the Specification:

  U.S. Patent Numbers: 
  5,634,064
  5,737,599
  5,781,785
  5,819,301
  6,028,583 

  In addition, the following patent is licensed on a
  royalty-free, non-exclusive basis for its term and for
  the sole purpose of developing software that produces
  PDF files that are compliant with the Specification
  (specifically excluding, however, software that consumes
  and/or interprets PDF files): 

  U.S. Patent Number: 
  5,860,074 

The long and short of that is that PDF is indeed Adobe-captive in a
sense until those patents expire -- but that Adobe freely licenses all
its patents for interoperablity purposes.  (The final patent cited 
doesn't seem to be an obstacle for applications reading in PDF input:
It covers a method for overlaying text over another layer.)


So, that's why we can have the GIMP, LaTeX, xpdf, pdfLaTeX, Kontour
(previously "Killustrator"), Ghostscript, etc. all able to handle PDFs.


Incidentally, also relevant to our in-person discussion:  I just noticed 
on-line that TIFF can be compressed with _either_ LZW compression or CCITT
Fax 4 compression, suitable for bitonal text documents.


[1] Interesting comments on graphics formats at:
http://memory.loc.gov/ammem/pictel/mddp309.htm
(Like Amy, somebody there's a real expert.)

[2] Of which the canonical example was as follows:  Open-source coder Avery
Lee announced in June 2000 on his now-vanished Geocities site for his Linux
program "VirtualDub":

  Today I received a polite phone call from a fellow at Microsoft who
  works in the Windows Media Group.  He informed me that Microsoft has
  intellectual property rights on the ASF format and told me that, although
  I had reverse engineered it, the implementation was still illegal since
  it infringed on Microsoft patents.  I have asked for the specific patent
  numbers, since I find patenting a file format a bit strange.  At his 
  request, and much to my own sadness, I have removed support for ASF in
  VirtualDub 1.3d, since I cannot risk a legal confrontation.

That turned out to be US Patent #6,041,345.  It's highly unlikely that an
obviously incompetently-awarded patent of a data format would survive legal
challenge, but Lee couldn't afford the cost of calling Microsoft's bluff.

Since then, a number of ASF open-source programs have emerged despite
Microsoft's threat -- some using mirrored copies of Lee's code.

[3] Adobe's disclosure documents to developers about PDF (including 
the PDF Reference document and the Patent Clarification Notice:
http://partners.adobe.com/asn/developer/technotes/acrobatpdf.html

-- Rick M.


----- End forwarded message -----

-- 
"The only thing is certain: Russian petty computer hooligans are very
slovenly, while FBI agents are very persistent in hunting them." --Pravda
	01234567 <- The amazing* indent-o-meter! 
        ^	    (*: Indent-o-meter may not actually amaze.)