Hi all, Nobody here is trying to discourage the use of micro sign. What character encoding are you going to use?
Micro sign (http://www.fileformat.info/info/unicode/char/00b5/index.htm) is single byte 0xB5 in Latin-1 (aka ISO-8859-1) but becomes double-byte 0xC2 0xB5 in UTF-8. There is also confusing Greek small letter mu (http://www.fileformat.info/info/unicode/char/03bc/index.htm) which is 0xCE 0xBC. In short this letter is bad for computer processing if we don't have mechanism to specify character encoding. UDUNITS 2 API has "encoding" argument, and users can choose either ASCII, Latin-1, or UTF-8. Accordingly "udunits2" command has options -A -L and -U. It is enough for library that users have control and responsibility. But CF is a standard of metadata that is exchanged among people to avoid confusion. The CF community can choose many ways. I'd like to see views on the community: (1) Create a global attribute to specify character encoding (like XML) I believe this won't work. (2) Declare that CF uses UTF-8 Probably many people simply ignore that and put single 0xB5 as micro sign. (3) Recommends only US-ASCII letters in "units" attribute Very conservative, but that is consistent with allowing only English in standardized attributes. (4) Do nothing I have to warn programmers to anticipate any byte pattern above. That would work if only micro sign is an extension to ASCII. Best Regards, -- Eiji (aka Eizi) TOYODA Japan Meteorological Agency / WMO/CBS/IPET-MDI On Sat, Mar 27, 2010 at 00:52, Andrew Clegg <[email protected]> wrote: > Hi Julien, > > I'm glad you brought this up. We had a discussion about this recently (look > for any threads with 'udunits 1 or 2 for CF' in the title): > http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2010/thread.html > > The best solution (in my opinion) was to use expanded names rather than > shortened, so instead of using 'u' (which has been replaced by 'µ' in > udunits2) you would use 'micro' (which is compatible with both). However it > would be nice to get a consensus on this or another solution, and some text > added to the conventions. > > Cheers, > Andrew Clegg > > > Julien Demaria wrote: >> >> Hi, >> >> I found the "u" micro prefix abbreviation in the current CF-1.4 >> documentation on units: >> >> http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.4/cf-conventions.html#units >> >> but it seems this prefix is not available in the last udunits-2 (udunits-1 >> is now deprecated) >> >> and in udunits-2 they break backward compatibility because the "u" symbol >> is now used for a new unit "unified_atomic_mass_unit", see in >> >> http://www.unidata.ucar.edu/software/udunits/udunits-2/udunits2-accepted.xml >> >> http://www.unidata.ucar.edu/software/udunits/udunits-2/udunits2-prefixes.xml >> >> So what is the position of the CF community concerning this point, is the >> "u" micro prefix CF-1.4 compliant or not? >> >> >> Thanks in advance, >> >> Julien >> >> _______________________________________________ >> CF-metadata mailing list >> [email protected] >> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > > > -------------------------------------------------------------------------------- > Plymouth Marine Laboratory > > Registered Office: > Prospect Place The Hoe > Plymouth PL1 3DH > > Website: www.pml.ac.uk > Registered Charity No. 1091222 > PML is a company limited by guarantee > registered in England & Wales > company number 4178503 > > PML is a member of the Plymouth Marine Sciences Partnership > Website: www.pmsp.org.uk > -------------------------------------------------------------------------------- > This e-mail, its content and any file attachments are confidential. > > If you have received this e-mail in error please do not copy, disclose it to > any third party or use the contents or attachments in any way. Please notify > the sender by replying to this e-mail or e-mail [email protected] and then > delete the email without making any copies or using it in any other way. > > The content of this message may contain personal views which are not the > views of Plymouth Marine Laboratory unless specifically stated. > > You are reminded that e-mail communications are not secure and may contain > viruses. Plymouth Marine Laboratory accepts no liability for any loss or > damage which may be caused by viruses. > -------------------------------------------------------------------------------- > _______________________________________________ > CF-metadata mailing list > [email protected] > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
