Subject: Re: List of Service Types

From: Stuart Cheshire <[email-masked]>
Date: Tue, 6 Aug 2002 21:24:07 -0700

>Yes, this is fine.    But on 98% of the printers like that that we have
>installed, my photo will come out in B&W (greytone).   Only one or two
>of the printers will actually print colour.   How does the laserwriter
>driver do on avoiding letting me (unintentionally anyway) send my nice
>colour image to a printer that simply cannot cope?

Are you asking about AppleTalk or DNS-SD?

Over AppleTalk, once the printer has been discovered using NBP, the 
driver talks to it using PostScript queries over PAP (the AppleTalk 
Printer Access Protocol) to find out more about its capabilities.

Using DNS-SD, the printer's TXT record contains some rudimentary 
information to identify simple capabilities, like whether it can print 
colour. This can save a subsequent connection to the printer to 
interrogate it directly.

However, and I have said this before, no attribute list can meet every 
application's requirements. Sure, the printer can print colour, but is it 
four-colour or six-colour? What is the ink chemistry? What is the gamut? 
What is the colour matching profile?

This is not a contrived example. At Stanford we had a high-speed 
black-and-white Xerox printer that could also overlay red toner. It was 
good for doing titles in red, and figures like pie charts, but useless 
for printing a full-colour photograph. If you are looking for a list of 
printers on the network that can print colour, should this printer show 
up or not? It's not a binary yes-or-no answer is it? It depends on what 
the user wants to print on it.

Stuart Cheshire <[email-masked]>
 * Wizard Without Portfolio, Apple Computer
 * Chairman, IETF ZEROCONF
 * www.stuartcheshire.org

---

From: Aidan Williams <[email-masked]>
Date: Wed, 07 Aug 2002 14:29:01 +1000

> colour. This can save a subsequent connection to the printer to 

Soo...  seems to me that a complete specification would need to
have templates for the TXT records along the lines that SLP has
schemas.  Or do you have something else in mind?

-- 

regards
	aidan
____
:wq!

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