[whatwg] Physical quantities: <var> or <i>?
Jukka K. Korpela
jkorpela at cs.tut.fi
Thu Apr 14 07:02:18 PDT 2011
Looking at the nice summary (with examples) of text-level markup at
I started wondering why there is no example of markup for symbols of
physical quantities. The descriptions of individual elements or their
examples don't seem to say anything about this either.
So what markup should we use for E = mc², given that by the applicable
standards, E, M, and c should appear in italics and the other characters as
Physical quantities surely satisfy the requirement that "typical typographic
presentation is italicized" in the following, and they are to be offset from
the normal prose, but why aren't they mentioned in the fairly long list of
"The i element represents a span of text in an alternate voice or mood, or
otherwise offset from the normal prose, such as a taxonomic designation, a
technical term, an idiomatic phrase from another language, a thought, a ship
name in Western texts, or some other prose whose typical typographic
presentation is italicized."
(As an aside, the wording "a taxonomic designation" is too broad, as by
biological nomenclature rules, genus and species names are to be italiced
but higher taxons, e.g. family names, like Canidae, must not. Besides, e.g.
an English name of a species is taxonomic too... So "scientific names of
organisms" would be a better formulation.)
But the i element should obviously be used in the absence of a more semantic
element; e.g., not for expressions that fall into the scope of use of the
Should we consider the var element as covering physical quantities too?
After all, they can be regarded as variables in a broad sense, as symbols
that denote different values in different situations. However, <var>c</var>
would be odd, wouldn't it, since the symbol denotes a universal constant of
So I would guess that <i>E</i> = <i>m</i><i>c</i>² is the way to go.
I think an example like this, or the addition of physical quantities into
the list of examples, or both, would be the semantics and intended use of
elements somewhat clearer.
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