Hyphens vs underscores in element names

Warren Hedley w.hedley at auckland.ac.nz
Wed Jan 26 05:26:49 GMT 2000


One of the more popular arguments between the development team for
FieldML regards a convention for the naming of elements and
attributes in our ML collection. The debate focuses over whether
we should use underscores (num_elements), hyphens (num-elements),
capitalisation (numElements) or runtogether (numelements). We've
eliminated capitalisation and runtogether because they don't
look as nice, and are now reduced to hyphens vs. underscores. The
older part of the development team is familiar with Fortran and C
and are keen to use underscores. However I've noticed in a brief
survey (results below) that most of the W3C-endorsed stuff seems
to feature minus signs.

Can anyone suggest any compelling reasons for going either way?
Does anyone want to add more data to my survey?

The Fortran coders also argued that there might be confusion with
arithmetic minus signs, if an application was to display something
like "mesh-1 - element-1", where "mesh-1" and "element-1" are
identifying attributes of type NMTOKEN (would have used ID but we
don't require uniqueness within a file). However since I cannot
prevent someone from using hyphens in an attribute value (without
resorting to schema validation), I don't think this holds. The
argument continued that users would be encouraged to use underscores
in identifiers if the element names also used underscores.

Begin Survey Results

Hyphens (last 2 not XML applications, but W3C) :

XSLT = <for-each>, <call-template>, etc.
XPath & XPointer = ancestor-or-self, etc
SMIL = <root-layout> @skip-content
W3C spec names = REC-DOM-Level-1-19981001
XHTML module names = xhtml11-tableb-1.mod

Underscores :

BioML = <dna_type> <keep_space> (not W3C)

Runtogether (I suspect this was chosen for legacy reasons ??) :

MathML = <maligngroup>
XHTML = <textarea> @colspan

Capitalisation (not all W3C WDs or Notes) :

XML-Schema = <unparsedEntity> @schemaName
SVG (Scalable Vector Graphics) = <animateMotion>
CDF (Channel Description Format) = <PublicationDate>
TEI (Text Encoding Initiative) = <docImprint>
OCS (Open Content Syndication) = <updatePeriod>

End Survey Results

In case anyone is interested, FieldML is a language for marking up
spatially and time varying fields, targeted at finite element
packages (in particular some software developed at Auckland called
CMISS). The development of FieldML can be followed here


Warren Hedley
Department of Engineering Science
Auckland University
New Zealand

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