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Re: FOP - what, where, when, how?


Alastair Growcott wrote:

> 
> I've heard and seen suggestions that PDF is an ASCII format, although
> when I open PDF files they seem to have a lot of encoded binary
> information. I also know that Windows opens .xml files in IE and that IE
> can display (or be told to display) files using Adobe Acrobat, and that
> XML files can specify an XSL file to use for display.

PDF is an ASCII format, but PDF docs can optionally use various
compression schemes for embeddedd graphics and for text. Thus, you
should be able to open any PDF document in a text editor, but most of
the data may look like garbage because it is compressed and then encoded
using a UUENCODE-type scheme.
 
> Is PDF an ASCII format, and if so can anyone point me at a description
> of it?

You can download the PDF spec from the Adobe Web site somewhere (not
sure of the exact URL).
 
> Rather than use FOP, would it be workable to have the XML file specify
> an XSL file to convert it to an XML file using XSL-FO, that in turn
> specifies an XSL file that converts it to a PDF file, and somewhere
> along the way have a line that tells IE to view it with Adobe Acrobat? I
> appreciate that this would be a lot of work, but very useful.
> Alternatively, for just my application, would it be workable to have an
> XSL file that converts my XML format files to PDF directly? I suspect
> that since there is no sign of anyone having done this that the answer
> is no, but figured it was worth asking.

As PDF is an ASCII format and has a pure ASCII (no compression) form,
you could, in theory, use XSLT to directly generate PDF. However, in
practice this would be very difficult if you need to do any kind of real
formatting because your XSLT would have to do all the geometry
calculations, as well as build all the different tables, dictionaries,
etc. that make up a complete PDF document. If you are just creating
something like database reports it is possible--you can find several
Java libraries that do this, for example. (For example, the Web site for
my 401 provider dynamically generates PDF reports for account
information, but the generated document is just a database report with
no complex formatting.)

The reason that page composition tools cost is because page composition
is hard.

If you are doing all the processing on the server you could have the PDF
generated on demand, although this could be slow for documents larger
than about 10 pages and would require pretty beefy servers if you have
any significant demand on the site. Probably not practical to do it on
the client as it requires various licensed, for cost tools, such as
Distiller.

Cheers,

Eliot

-- 
W. Eliot Kimber, eliot@isogen.com
Consultant, ISOGEN International

1016 La Posada Dr., Suite 240
Austin, TX  78752 Phone: 512.656.4139

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