Gregor Hagedorn, 04/04/2013 11:39:
If an editor saves a page with
{{#property:population}} the parser
looks up the current value and changes this to:
{{#property:population|current value=2348732}}
and stores this wikitext version in the Wikipedia. The same would
apply to updating, saving {{#property:population|current
value=2348732}} may result in {{#property:population|current
value=2348700}} being saved.
A middle ground would be using the qualifiers for something like
{{#property:president|as of=2013}} which would always transclude the
president of /this/ mandate. However you'd still have to pass this
parameter in any call for a template where the property is transcluded,
while such stuff is often implicit. The problems Daniel describes are
hardly resolved. (This said knowing nothing about the syntax, qualifiers
etc. Sorry.)
Nemo