Case conventions on element names?

Question

Are there any formal recommendations on element casing in XML?

I know XHTML uses lowercase element names (as opposed to HTML which canonically uses uppercas

Answer 1

To expand on my comment above: the use of 'lowercase with hyphens' has some problems in XSLT. Specifically it is easy to confuse a node called, say, 'year-from-age' with a formula 'year - age' (e.g. subtract age from year).

As @KarlKieninger points out, this is only a problem at the human level and not for the XSLT parser. However since this will often not produce an error, using 'lowercase with hyphens' as a standard is asking for trouble, IMHO.

Some pertinent examples:

<a>1</a><b>1</b>
<xsl:value-of select="a+b"/>
outputs 2, as expected

<a>1</a><b>1</b>
<xsl:value-of select="a-b"/>
DOES NOT ERROR, BUT OUTPUTS NOTHING AT ALL

In the above code, you must put at least one space before a subtraction operator, but there is no such requirement for an addition operator.

<a-b>1</a-b><c>1</c>
<xsl:value-of select="a-b -c"/>
outputs 0, as expected

But note how confusing the above is to read!

<a>1</a><a-b>3</a-b><b>2</b>
<xsl:value-of select="a-b"/>
outputs 3

<a>1</a><a-b>3</a-b><b>2</b>
<xsl:value-of select="a -b"/>
outputs -1

The presence of a single space changes the output above, but neither variant is an error.

Answer 2

Google's style guide recommends (perhaps even mandates) camelCase for all element names, as well as attribute names.

Answer 3

The original intent for XML casing was lower case with hyphens. It's case sensitive and doesn't require you follow that convention -- so you can do whatever you want. I have no citations, sorry.

Answer 4

Not that it matters, but I've always been partial to PascalCase for Elements and camelCase for attributes:

<Root>
  <ParentElement attributeId="1">
    <ChildElement attributeName="foo" />
  </ParentElement>
</Root>