Re: atoms, molecules

["Simon St.Laurent" <simonstl@simonstl.com>]

At 04:41 PM 4/17/01 -0400, Steve Rosenberry wrote:
>If I understand what Simon wishes to do, it is similar to what I wished
>for in a late March post to this list and also in comments I made to W3C
>requesting a regular expression syntax that allowed datatypes to be
>defined as regular expression atoms.  The start of the thread can be
>found at:
>
>http://lists.w3.org/Archives/Public/www-xml-schema-comments/2001JanMar/0425.html
>
>The thread continues in the April to June comments at:
>
>http://lists.w3.org/Archives/Public/www-xml-schema-comments/2001AprJun/0008.html

Yes, it's very similar.  I think there are some likely syntactic difference 
in what I'm pondering and what you presented, since I'd do the 
fragmentation first and then specify rules for the atoms, but we're in 
about the same place.

>My motivation was to specify an attribute as a numeric value with units
>of measure attached to it for absolute clarity.  (Ask NASA how important
>this might be.  They lost a Mars probe because numbers had no units
>associated with it and one group assumed metric while the other group
>was specifying English.)

Units of measure are another good case for this, and they tie well into 
Kohsuke KAWAGUCHI's question about definining the rules governing 
relationships between these atoms.  It could make it very easy to handle 
inches->cm, for instance.

>Using a pattern restriction as a template to identify atoms of interest
>within an attribute is similar to the ordering of elements in a
>structure.

Exactly, though you only have a sequence of character to work with.

>Is it redundant?  Maybe.
>
>Is it "good" markup?  Probably not.

Not as defined by people who see one data structure, one markup 
structure.  But since no one seems to want to write:
<date><year>1970</year><month>11</month><day>25</day></date>

it's a real problem worth addressing.

>Is it a useful, alternative way to specify information?  I believe so.

Definitely.

>Since the only guideline for when one should use attributes vs. elements
>is "It depends upon the application.", I don't see this further
>structuring, parsing, and use of attributes as fundamentally wrong given
>that it has clear functionality for certain developers and users of XML.

Yep.  I think it's probably worth going ahead with a larger-scale 
exploration of the possibilities.  This doesn't appear to be the opinion of 
the Schema WG, if Noah Mendelson's reply to your proposal is to be believed:
http://lists.w3.org/Archives/Public/www-xml-schema-comments/2001AprJun/0045.html

However, I think it's pretty clear that there's room in the world for 
further experimentation.


Simon St.Laurent - Associate Editor, O'Reilly and Associates
XML Elements of Style / XML: A Primer, 2nd Ed.
XHTML: Migrating Toward XML
http://www.simonstl.com - XML essays and books