Hi Michael,
Have you been thinking if OpenJUMP should support NULL as a third option in
Boolean attributes? Right now it seems to partly support NULLs, partly not.
- Create a new feature, do not edit attributes, save -> Boolean
attributes are saved as NULLs but user probably believes that they are False
because attribute table shows the box unchecked.
- Edit Boolean attribute by checking/unchecking the tick box -> Value
is True or False but it can't be changed back to NULL
Current behavior does not feel correct. I can imagine two alternatives:
- Deny NULL and initialize all Boolean attributes to False.
- Make some clever change to user interface that makes difference
between the three Boolean values: NULL, TRUE, FALSE. Empty check box with
colored borders for null? Or three-item drop-down menu?
Considerations about what it means on the Java side
http://stackoverflow.com/questions/11185321/when-should-null-values-of-boolean-be-used
dBase format and shapefiles do support NULL
http://www.clicketyclick.dk/databases/xbase/format/data_types.html
-Jukka Rahkonen-
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