And I (still!) very strongly disagree. The empty set symbol stands
for the empty set (also written {}). But there is no set here, let alone
an empty one. Possibly an empty string (of phonetic symbols?).
Written as '' or "" in your favourite programming language, and
conventionally written as a lowercase epsilon (ε) in math contexts.
(That does not make the empty string equal to a string consisting
of the letter ε, of course!)
No one claims that empty set symbol used by logicians for empty set is used by linguists with exactly the same meaning.
The glyph ! is use by mathematicians to indicate "factorial", by phoneticists to indicate an aleveolar or postalveolar click, and by programmers in c and some other programming languages to indicate "not".
Such overloading of symbols between disciplines (and even within disciplines) is common.
But capital "slashed o" (U+00D8) is not mentioned... And that letter
would be entirely appropriate for this purpose **in the contexts** where
it would stand for a "null consonant" (or empty string) in linguistics.
It is not clear to me why the empty set symbol, which at least as the idea of emptiness associated with it, should be more inappropiate for use in linguistics for null character(s) than capital O-slash (Ø) which is a consonant in a real language and as such as no suggestion of emptiness about it, especially not to linguists who recognize its lowercase form as part of IPA.
Also, linguists might be dealing with Norwegian and may wish to use actual Norwegian spelling in their explanations.
But capital "slashed o" (U+00D8) is not mentioned... And that letter
would be entirely appropriate for this purpose **in the contexts** where
it would stand for a "null consonant" (or empty string) in linguistics.
Almost *any* character not otherwise used could be appropriate **in the contexts**.
It does not appear to have wandered into linguistics in any way (except by occasional typographic mistake, and that does not count), even though there is use of a similar-looking symbol.
Can this supposition be documented?
I thought the opposite, that the slashed zero form that sometimes appears in linguistics was a variant mathematical null set symbol, that the evolution was the opposite to what you suggest.
I think it would be less problematic to use the letter Ø for the empty
set (in a math context), than to use the EMPTY SET symbol (Ø) for any
linguistic entity in a word-like linguistic context.
But it *is* being so used and has been used for quite some time. The word "problematic" is puzzling. What problems does this usage cause?
From the web page http://www.cl.cam.ac.uk/~mgk25/ucs/secs.html by Markus Kuhn on the empty set symbol:
# Used in technical drawings and on product descriptions. Note that # DIAMETER SIGN is an exact circle while EMPTY SET is often a digit zero, # both with a stroke.
Markus Kuhn distinguishes the diameter symbol from the empty set symbol but considers slashed zero as just a variant of the empty set sign, presumably from the same kind of glyph variation I have also seen in practise and which Ken Whistler commented on.
The web page http://www.brl.org/formats/rule18.html provides official Braille translations for IPA type symbols, including a braille symbol to be used for either the slashed zero or round slashed circle glyphs with the notation:
slashed zero, null or empty set
Personally I prefer the slashed zero for null character(s) in linguistic contexts.
I don't know if it also occurs in mathematical contexts as a null set symbol.
Whether in linguistics the slashed zero should be considered a glyph variant of the mathematical empty set sign or whether the slashed zerio is a symbol unto itself (distinct from both the empty set sign and normal zero) is something for practising linguists to argue over or agree on.
That the slashed zero glyph (used for null character(s) in linguistic texts) is to be distinguished from normal zero in linguistic texts is easy enough to demonstrate.
Are there also linguistic texts that distinguish slashed zero from the mathematical empty set sign, giving different meanings to each?
If so, then someone who wishes for Unicode to include slashed zero as an independant character should make a formal proposal to Unicode with sources to back up the difference in use.
Even if linguists in general feel that the empty set form which often appears for (null character(s)) is a kludge for the proper slashed zero empty character symbol, a reasonable proposal could be presented, backed by one or more linguistic organizations.
At least slashed zero might be made available as a variant of the round empty set symbol through a variation selector ... if it is *asked for*.
But that is for those who use such notation regularly to decide.
But I doubt you will find any linguist who would consider the Norwegian capital slashed O as anything other than a kludge replacement for either the standard round empty set symbol or the slashed zero symbol.
Jim Allan
