[sc34wg3] TMQL: Proposal to drop the "characteristics" axis

[Lars Heuer]

Hi all,

A year ago I made an example that shows that the "characteristics"
axis can be replaced with a postfix filter (c.f. [56] filter-postfix)
[1].

And the more I think about the idea the better I like my idea. ;)

I find the "characteristics" axis cumbersome for the following
reasons:
- Loooong name (easy to introduce typos)
- TMDM does not define "characteristics", it's a XTM 1-legacy term
- Can be replaced with postfix filters without loosing anything

Here some examples from the TMQL spec. dtd. 2008-07-15:

1.
  jack >> characteristics tm:occurrence

  Replacement:  jack / tm:occurrence

2.
  jack >> characteristics nickname

  Replacement: jack /nickname
  or (to ensure that names are returned): jack /nickname [. isa tm:name]

3.
  jack >> characteristics tm:subject

  Replacement:  jack /*


Personally, I find the replacements much more readable.

One problem remains: How to travel from an occurrence / a name to the
parent topic? If we'd introduce '..' as navigation to the parent
(similar to XPath), this problem can be solved.

Side note: Imo the description of the "characteristics" axis is
suboptimal:

          """
          If the value is a name or an occurrence item, in backward
          direction this step computes the topic to which the name or
          the occurrence is attached
          """

It gives the impression that just one topic is returned, but a
sequence of topics is returned:

   "Puck die Stubenfliege" << atomify  << characteristics tm:name

would return all topics which have a name "Puck die Stubenfliege", not
only one.

[1]
<http://www.isotopicmaps.org/pipermail/sc34wg3/2007-October/003429.html>

Best regards,
Lars
-- 
Semagia 
<http://www.semagia.com>