Empty IA5String

["Kurt D. Zeilenga" <Kurt@OpenLDAP.org>]

It's my opinion that IA5 String values should have
non-zero length.  Non-zero length values were
explicitly precluded for many attributes of
IA5String syntax (see RFC 1274).  Removing this
restriction would cause breaking.

It is debatable whether RFC 1274 implied a general
restriction that IA5 String values be non-empty,
however it seems most agree that it not clear what
the semantics an empty value would have.

Those in favor of allowing empty IA5 values have
primarily argued that the empty value is useful
to represent no values.  Traditionally, in X.500,
no value is represented by having no values.
Some have also that an application could regard
empty values as being a "default" value.
Traditionally, " " has been used for such purposes.

In either case, it likely that many clients would
not regard an empty string as having one of these
semantics, but as simply being invalid.  That is,
an zero-length 'foo' attribute is far more likely
to be regards as an invalid foo than as either no foo
or a default foo or some other foo.

I also note that a number of programming languages
do not handle well zero-length values, often be confused
as no value.

For these reasons, I suggest that the IA5 string syntax
be revised to preclude zero-length values.

Kurt