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Re: CIF or NOT CIF, (or nothing)


> The aim of ("imageNCIF") is to "standardize" the passing of image (and other) 
> crystallographic experimental data (1) from: one institute to another;
> one make of computer system to another; and from one computer program 
> (acquisition or analysis) to another (2). If a sufficiently large number
> of institutes/ programmers/ and producers of detector equipment can
> agree on a common format then the present task of having to support 
> numerous new and different image (data) formats will be at least 
> lessened (3).

(4) The aim is also to be able to archive images. For instance at the ESRF, 
the production of numerized image at the topography station will be thousands 
per year. Thus we need a format for archives linked to a good software for 
databases.

> 
> Notes:
>  
> 2. This implies an inter-continental scope.

It also means that images should be easily transfered through the network. A 
scientist working at a given place should be able to load his/her images at 
another place.

> 
> 3. This implies that the format must be flexible enough to cover a variety
>    of needs. However, does not mean that every conceivable need must be 
>    addressed (immediately).

The format should be flexible enough to be able to progressively follow new 
needs.

> 
> -------------------------------------------------------------------------------
> 
> I think it would be useful to have everyones views on the 3 proposals
> raised by Brian, plus the proposal to base any format on something which
> is NOT CIF in the strict sense. And in fairness to certain views, I also
> add a 5th "proposal": "Do nothing". So can I ask everyone to at least give a
> comment on the 5 choices (or on others), concerning the basic support 
> mechanism for the file format:
> 
>   1: CIF based, using encoding to convert binary data to ASCII

Let me be straight. There is no future in any ASCII encoding, for the image 
itself. ASCII encoding does not add any advantage for archives and makes the 
files much bigger. 

What is the inconvenient in binary encoding of the data?

- Transferability? 
Today ftp exists everywhere and allows binary transfer. The lengthy battle 
between ASCII and EBCDIC and limitations in transfer is over.

- Readability in the future?
An image is a set of:
  + 1 to four bytes integers
  + real numbers
  + complex numbers
Thus it is a set of bytes. Assume that tomorrow the standart changes to encode 
any of these numbers, it will never be very difficult to write programs to 
decode a flow of bytes for this new format, as long as we know what is the 
kind of contents. This should be part of the header of the image.

For instance, today I have no difficulty in exchanging images between a Cray 
and an IEEE computer.
 
> 
>   2: CIF based "header file", using file pointers to point to binary file(s)

This is the wise solution. There is no reason to encode the header with 
something different from ASCII. 

For our purpose we have established our own format. In the first version the 
header was binary encoded. It is now ASCII.

This allows to read the header without any conversion, with any utility 
(including a text editor) and will make the link to a database software easier.

> 
>   3: CIF based "graphics" description of binary data

I do not understand to well the use of graphics for images. 

> 
>   4: Break with existing CIF to at least some extent, probably because a
>      file contains binary data. This could be "CIF" sections within a binary
>      files, or could be any other non-CIF format.

Please explain the difference with 2.

> 
>   5: Do nothing. 
> 

The existing formats do not allow to add all the information which sould be added to any image for archiving and/or further tretment and use.

I believe the good solution is 2.


Best regards,
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       :    Yves EPELBOIN                                          :
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