[whatwg] [WA1] 2.7.13: sub and sup

Ian Hickson ian at hixie.ch
Mon Dec 10 20:33:05 PST 2007

On Sun, 28 Aug 2005, dolphinling wrote:
> I would like it if the section on sub and sup included text along these lines:
> | The semantics of sub and sup are weaker than those of elements in
> | some other languages, e.g. MathML's msup. Authors should when possible
> | use those other languages instead of sub or sup.

The spec currently has this as markup:

  <p>Mathematical expressions often use subscripts and superscripts.
  <!--Authors are encouraged to use MathML for marking up mathematics,
  but authors may opt to use <code>sub</code> and <code>sup</code> if
  detailed mathematical markup is not desired. <a
  href="#refsMathML">[MathML]</a>--></p> <!-- XXX -->

The problem is that there's no point telling authors to use, say, MathML, 
when in fact they can't (since only one browser supports it).

> Actually, I think the semantics of sub and sup are nonexistant

Clearly they're not completely non-existent, since this:


...and this:


...and this:


...are three very different things.

> but I think this allows authors to use then when needed (e.g. when they 
> need IE6 support) while providing strong enough reinforcement of the 
> fact that better, more meaningful ways exist. (And while avoiding 
> avoiding arguments among us standardisers about whether or not they have 
> semantics, because whether or not they do, they're inarguably weaker :-)

Well, what would you replace them with? The only form at MathML that has 
any support in browsers is presentational MathML anyway, which isn't that 
much better, "semantically".

> Also, a few more comments on the section. While MathML is obviously the 
> best-known and probably most important language using sub/superscripts, 
> I think it should be noted that others (e.g. ChemML) exist, even if not 
> noted by name.

ChemML enjoys even less support...

> For me, saying "sub and sup" is much more natural than "sup and sub". 
> I'm not sure why this is, but the HTML 4 spec has it sub first, too. 
> Would you mind switching it to this way in WA1?


> And finally, "Authors are encouraged to use MathML for marking up 
> mathematical, but authors may..." <-- I think you're missing a word in 
> there.

Fixed (as noted above).

Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'

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