🚀 go-pugleaf

As for PostScript vs. DDL, I quote from the March 1987 IEEE Spectrum
magazine article "Desktop publishing: what it can and cannot do" by
Ronald K. Jurgen

     Among the typical page description languages available today for desktop
     systems are Adobe System's PostScript and Xerox Corp.'s Interpress.
     Instead of a page description language, a document-composition language
     like Imagen Corp.'s DDL may be used.  It conveys the format of a full
     document to the printer rather than describing only one page at a time.

Sounds like DDL is a somewhat different beast...
-- 
		Scott Simpson
		TRW Electronics and Defense Sector
		...{decvax,ihnp4,ucbvax}!trwrb!simpson

Since there are few people who have actually seen an Interpress and/or DDL
printer, it's hard for anyone to say anything that isn't based on some
manufacturer's claim or second-hand knowledge.

That said, now I'll give all of you the benefit of my second-hand knowledge
and manufacturer's claims (;-):

Xerox says that Interpress is designed for speed and is faster than
PostScript.  Considering that the only version of Interpress that's
available now doesn't do graphics, only text and scanned images (no
vector graphics, clipping, or rotation of text), I can see why it's fast.

Xerox also says that Interpress is "a printing architecture that clearly
distinguishes the process belong on the printing domain from those in the
document creation domain.  By placing many decisions on the computer's
side, Interpress increses printer efficiency.  In addition, by requiring
greater structure in a master, Interpress limits the application from
creating a master that would consume unnecessary amounts of processing
time at the printer."  Read that any way you want, to me it means that
Interpress gains speed by giving up some flexibility.  Interpress does
support printing over Xerox' XNS network.

The document that Xerox sent me was printed on a Xerox 8044 printer over
XNS.  The font is a san-serif; it looks nice, has good letterspacing and
overall is more than acceptable.

I'm posting a message about DDL that Geof Cooper at Imagen originally posted
to the net last September.  I can't vouch for the validity of any of the
statements in that posting; however, I can say that there is one inaccuracy:

>DDL allows for user selection of both linear and nonlinear scaling of fonts.
>It is the only description language with this capability.

PostScript also allows for nonlinear scaling of fonts (see "Tips and Tricks",
The PostScript Language Journal, 1Q87, pp. 37-40).

I think that DDL's most important feature is its ability to define graphical
objects that are precompiled by the interpreter.  If this also means that
the object is cached as a bitmap, then some applications will run much
faster under DDL compared to PostScript if they use the same graphic many
times.  (Don't write back to me telling me about the PostScript font cache.
It does effectively the same thing; however, you have little control over
what goes into it except the maximum size of the character cached.  With
a large enough font cache, you could, in fact, cache graphics; however,
that's not quite the same thing.)  If this allows caching of halftones
(which can't be done in PostScript, and I'm not sure if you'd really want
to do it anyway, since you want your halftone screens to line up...) then
certain applications that use halftones over will run faster with DDL.
(You reading this Dave Y?)

Pat Wood
Editor, The PostScript Language Journal

[[Editor's note:  I have decided not to resend the old list message
from Geof Cooper because of its size.  I think that understanding this message
and the current discussion does not depend on this older message.
				--Rick ]]