[OSM-talk] Tagging schema

Lester Caine lester at lsces.co.uk
Mon Oct 5 10:28:45 BST 2009

Andrew Errington wrote:
> On Mon, October 5, 2009 15:36, Lester Caine wrote:
> <snip>
>> ( Egil - a little aside, while a check box for boolean would be nice,
>> there is still an element of 'NULL' - that is in addition to setting a
>> boolean tag, one still needs to decide if it should or should not be
>> present )
> Checkboxes these days /can/ represent three states.  There are usually two
> states: checked (or ticked) and not checked (an empty white box).  In most
> GUIs it is possible to represent a third state, perhaps a grey square
> filling the box.  (This is different from the control being disabled,
> usually shown by being greyed-out).  The meaning of this third state
> depends on the application, but it can mean NULL, unknown, conflicting
> source data, or whatever you want it to mean when it's not True or False.
> I'm not sure that this third state is particularly useful or intuitive,
> but I know it means something different to True or False when I see it.

Your missing the point Andrew - we need to be able to 'switch the tag on 
or off' as in Add it or not to the current object. We would not expect 
every 'boolean' tag to be presented, so need to be able to select it, 
and then also delete it again if appropriate.

In my terms 'NULL' just means not present at all, but if it was a tag 
that has a default interpretation, then it may be added automatically 
anyway? But need not be present to flag it's default state.

Lester Caine - G8HFL
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