'itemprop' and 'rel' attributes on

问题:

Is it valid to use the itemprop attribute and the rel attribute on the same element?

The example from Google’s Site Name documentation contains

<link rel="canonical" href="https://example.com/" itemprop="url">

which gives this error in https://validator.w3.org/nu/:

Attribute rel not allowed on element link at this point.

回答1:

It depends on the specification.

Microdata, where the itemprop attribute is coming from, is defined by WHATWG’s HTML as well as by W3C’s HTML Microdata.

The WHATWG version is a living standard without snapshots (so things might change; my quotes are from 2015-07-25), the W3C version is currently only a Working Group Note from 2013, no Recommendation.

For the a element and the area element:

• both specifications allow to use the attributes itemprop and rel together

For the link element:

• WHATWG: it’s disallowed to use the attributes together

  link element:

  A link element must have either a rel attribute or an itemprop attribute, but not both.

• W3C: it’s allowed to use the attributes together

  Content models:

  If a link element has an itemprop attribute, the rel attribute may be omitted.