The Dublin Core Metadata Initiative (DCMI) is an open source movement that aimed to standardise data on the web regarding digital objects and entities. Which is great until it doesn’t validate as well-formed HTML5..

Dublin Core HTML5 Microdata

Using Dublin Core on your site involves adding a separate set of metadata properties alongside any existing rich snippets you may already have. Adding it onto your website allows search engines to gather more data about your site and its content. It provides an additional layer of information for the constantly changing semantic web and adds more semantic value to your website for search engines, like Google, to then use and factor into their ranking.

If you’re wondering why you’d need to implement any microdata on your website; Google has expressed that it is dropping support of the meta keywords tag as a method of gathering some understanding about your content and their target keywords, rather, it’ll interpret your keywords based on your website content. This doesn’t mean that with additional structured data / rich snippet integrations, search engines will favour you any less but the more data you make available about your content and your website, the more search engines have to interpret.

This is where Dublin Core becomes so useful, not too dissimilar from, you’re able to integrate rich snippets of data within your document body and provide some further semantic knowledge and information behind the website pages and their content which should aid your overall website SEO and rankings across search engines.

Implementing Dublin Core is easy, it doesn’t bloat your website and is part of a coding standard (if only it validated natively..), so in theory, it won’t become outdataed any time soon (though that isn’t to say the likes of won’t become superior to it).

If you’ve already got Dublin Core on your website, you’ll hit an error when trying to validate your page and if you’re running any online SEO checking tools they’ll all feedback that your code is invalid. Why?

Error: Bad value schema.dc for attribute rel on element link: The string schema.dc is not a registered keyword.
​<link rel="schema.dc" href="" />

Why? The link type schema.dc isn’t registered as part of the HTML5 specification under the ‘link type extensions’ section as it doesn’t conform to the requirements in the specification. So technically speaking, using the schema.dc or schema.dcterms namespaces are invalid. So how do you get around this?

It’s pretty easy. HTML5 allows you to prefix your document with an XML / RDFa namespace which is perfect for the likes of Facebook, OpenGraph and Dublin Core.

So we change our implementation from having this in the <head> section:

<link rel="schema.dc" href="" />
<meta property="dc.title" content="Website Title" />
<meta property="dc.description" content="Website Description" />


<html lang="en-GB" itemscope itemtype="">
<head prefix="og:; dcterms:">
<meta property="dcterms:title" content="Website Title" />
<meta property="dcterms:description" content="Website Description" />

Running the HTML5 validator will now pick up the DC schema, prefixed by ‘dcterms’ meaning you can use the syntax:

<meta property="" content="Value" />

Alongside OpenGraph, you'll need the following:

<meta property="og:title" content="Website Title" />
<meta property="og:description" content="Website Description" />

And finally, with, you get:

<!-- Dublin Core -->
<meta property="dcterms:title" content="Website Title" />
<meta property="dcterms:description" content="Website Description" />
<!-- Open Graph -->
<meta property="og:title" content="Website Title" />
<meta property="og:description" content="Website Description" />
<!-- -->
<meta itemprop="name" content="Website Title" />
<meta itemprop="description" content="Website Description" />