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Query on Unicode and IGES Character Set


CAMAX (Your NC Programming Partner) is looking at using Unicode for
internal text string representation. It appears that Unicode is part
of a general solution that will last well into the future for our
internationalization efforts across multiple platforms and operating
systems. In examining Unicode, though, we've come across some questions
that may seem basic to the Unicode experts, but please bear with me.

An important feature of our software is the ability to read in IGES
(Initial Graphic Exchange Specification or some such meaning) files.
These files contain CAD data.

The problem is that IGES, an ANSI standard, uses an odd character
set that contains some characters I cannot find in the Unicode
Standard Vol. 1. In addition, Unicode contains some characters,
particularly in the math section, that look like the IGES characters.
But, I'm not sure if I should be using the Unicode characters for
alternate meanings. The reason why I'm not sure is that IGES defines
some particular meanings to these symbols.

To get specific, The following IGES characters seem to have close
Unicode equivalents:

Unicode                          IGES

U+2197 Upper Right Arrow         Circular Runout     FC 68 (1001, 1003)
U+2205 Empty Set                 Diameter            FC 6E (1001, 1003)
U+2248 Almost Equal To           Approx. Equal       FC 6E (1002)
U+22A5 Up Tack                   Perpendicularity    FC 6C (1001)
U+2295 Circled Plus              Position            FC 6A (1001, 1003)
     (In the IGES character, the plus extends beyond the circle. In
      U+2295, the plus does not. CAD folks are usually very picky about
      these things.)

(IGES seems to map all these characters into the ASCII range
using a set of code pages: 1, 1001, 1002 and 1003. My knowledge of
IGES isn't that great, though.)

I'm not surprised that cylindricity is not part of Unicode, but Diameter
seems like it should be included.

In addition, there's some odd IGES characters that I can find no
match (close or otherwise) in Unicode, including:

* Total Runout FC 74 (1003), which looks like a horizontal bar at the
bottom of the character, with a arrow going in the North East direction
coming from each end of the horizontal bar.

* Cylindricity FC 67 (1001, 1003), which looks like a small circle
(centered in the character cell) with two parallel diagonal lines
going from the bottom of the character cell and touching the bounds
of the circle. These lines go in a North East direction.


More questions: Since IGES is a standard (at least in the USA) and it
defines a character set, is there any efforts to map this set to
Unicode? We'd like to use any standard (including de facto standards)
in this area. If not, why isn't Unicode addressing this? (I'm curious
why, not complaining.)

Surely we're not the only company addressing CAD/CAM data in IGES files.
How are other firms dealing with IGES and Unicode?

If you have any information on this at all, please send responses to
johnsone@camax.com (please note the "e" in my email address). I'll do
the work of summarizing and then mail the results to this list.

Thanks,
-Eric

--
Eric F. Johnson           email: johnsone@camax.com   ERROR_TOO_MANY_SECRETS
CAMAX Systems, Inc.       phone: +1 612 854 5300      -The maximum number of
7851 Metro Parkway        fax:   +1 612 854 6644      secrets has been
Minneapolis, MN 55425 USA                             exceeded.-Win32 (NT) API.