Re: [ddlm-group] Relationship of CIF2 to legacy platforms

We should resolve the Fortran line length issue as I think we've got
enough information on the table - could those who haven't indicated
their preference please vote either

(1) CIF2 should have a maximum line length specified or
(2) no line length should be specified.

For bonus points, you can indicate what this length should be.

So (including Nick's recent email) I count the votes as:

(1) Herbert (>=2048), Nick (2048), James (4096)
(2) Joe

I've added my vote to the fixed line length simply because I accept
Herbert's argument that legacy Fortran programs are actually important
in the crystallographic world, and a restriction on line length does
not impose a burden on CIF readers.  It also imposes a bit of
discipline on CIF writers and helps to produce a readable file.

On Fri, Nov 13, 2009 at 3:47 AM, Joe Krahn <krahn@niehs.nih.gov> wrote:

Nick Spadaccini wrote:

On 3/11/09 12:53 AM, "Joe Krahn" <krahn@niehs.nih.gov> wrote:

Herbert,
I am only suggesting that maintained Fortran code ought to be able to
utilize F2003 STREAM I/O, supported by current versions of GFortran,
Intel Fortran and Sun Fortran.

Of course, I probably am not considering all of the issues. STREAM I/O
avoids the need for a fixed maximum record length, but even the newest
Fortran compilers have very limited UTF-8 support. Even with STREAM I/O,
it is not trivial to count trailing blanks as significant.

Maybe the biggest problem is UTF-8. IMHO, it makes sense for UTF-8 to be
an optional encoding, rather than just declaring CIF2 is all UTF-8. This

Not sure what you gain by doing this. If it is pure ASCII only then the
declaration of UTF-8 inhibits nothing, since ASCII is a subset. If it is not
pure ASCII, then it needs to be UTF-8. I can't see how knowing in advance
that it is a subset of UTF-8 or possibly the full set of UTF-8 gives you
anything.

cheers

Nick

A compiler/language not aware of UTF-8 could avoid errors by rejecting
CIF files that contain UTF-8. However, I think the approach being taken
is just to allow implementations to restrict usage, rather than put it
in the specifications. For example, the plan seems to be that
DDL/dictionary definitions will be used to avoid UTF-8 in data names,
where it is most likely to be a problem. So, you are right: there is no
reason for the CIF2 syntax to make UTF-8 optional when the dictionaries
can restrict characters to the ASCII subset.

The other potential legacy issues I know of are fixed maximum line
lengths, and significant trailing blanks. Dictionary definitions cannot
avoid these. It might be possible to take a similar approach, by
avoiding them by implementation conventions rather than making it part
of the spec. If these are only going to be an issue for a few more
years, it would avoid having to make another syntax change in the near
future.

My main interest here is to avoid incompatible implementations. I also
think that Fortran, and any other line-oriented I/O software, should be
able to do stream-oriented I/O in the near future.

Joe

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