Discussion List Archives

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [ddlm-group] LOOP versus LIST

A list with lists nested to arbitrary depth can be a single data 
value either in a loop or just for a single tag.

DDL2 make no distinction between a one-element loop and the same unlooped
tag with the same value.  DDL1 (see _list) and DDLm (see 
_definition.class) try to make a distinctions among things that are 
and are not permitted to be looped.

I do not understand why it is desirable to make such a distinction for
a single row table, following the DDL2 approach of allowing it
to be handled as either

   _xxx.aaa data1
   _xxx.bbb data2
   _xxx.ccc data3

or

loop_
   _xxx.aaa
   _xxx.bbb
   _xxx.ccc

   data1  data2  data3

seem harmless to me, but DDL1 and DDLm make the distinction and a proper
parser should note violations of what was specified for the category.

An index key is not a name, but a string, so I think it reasonable to
accept the empty string as a table index value.

Case sensitivity is an interesting question.  I would prefer case sensitive
table indices, but I suppose that matter should be discussed.



At 12:41 PM -0500 1/5/10, Joe Krahn wrote:
>I assume that a list of items defined via a loop is distinct from a list
>of items defined by a list. Is that correct?
>
>Likewise, is a list of one item distinct from a scalar value?
>
>Currently, CIF files don't differentiate between a one-element loop and
>a scalar. For example, RCSB components.cif does not use loops for atom
>data when there is only one atom. Is this stated anywhere?
>
>Also, is an empty string a valid TABLE index? Other CIF names require at
>least one character, but my understanding is that a TABLE index is any
>valid string, which includes an empty string. Strings are also
>case-sensitive, so I assume that TABLE indices are also case-sensitive.
>
>Thanks,
>Joe Krahn
>_______________________________________________
>ddlm-group mailing list
>ddlm-group@iucr.org
>http://scripts.iucr.org/mailman/listinfo/ddlm-group


-- 
=====================================================
  Herbert J. Bernstein, Professor of Computer Science
    Dowling College, Kramer Science Center, KSC 121
         Idle Hour Blvd, Oakdale, NY, 11769

                  +1-631-244-3035
                  yaya@dowling.edu
=====================================================
_______________________________________________
ddlm-group mailing list
ddlm-group@iucr.org
http://scripts.iucr.org/mailman/listinfo/ddlm-group

Reply to: [list | sender only]
International Union of Crystallography

Scientific Union Member of the International Science Council (admitted 1947). Member of CODATA, the ISC Committee on Data. Partner with UNESCO, the United Nations Educational, Scientific and Cultural Organization in the International Year of Crystallography 2014.

International Science Council Scientific Freedom Policy

The IUCr observes the basic policy of non-discrimination and affirms the right and freedom of scientists to associate in international scientific activity without regard to such factors as ethnic origin, religion, citizenship, language, political stance, gender, sex or age, in accordance with the Statutes of the International Council for Science.

Useful links