Semantic SEO: What is the difference between schema.org and Microdata?

Often, developers being new to schema.org and the usage of semantic SEO techniques are confused about the relationship between schema.org and Microdata, Microformats, RDFa, GoodRelations, and other standards.

Here is a quick explanation that I have been given so often that I assume it may be useful for others:

When you expose structured data from within Web content by adding extra markup to HTML content, you have essentially two components:

1. A vocabulary (also known as data schema, ontology, data dictionary, depending on the background of the people you speak to): This provides global identifiers for types of things (“Product”, “Car”, “Restaurant” – often called “classes” or “types”) and for properties (e.g. “screen size”, “weight” – often called properties or attributes)

2. A syntax for publishing the data within Web pages in HTML. The syntax is the convention for the actual characters used to publish a piece of data. Relevant syntaxes in here are RDFa, Microdata, and recently JSON/JSON-LD.

Popular vocabularies on the Web are schema.org, GoodRelations, FOAF, SIOC, and a few others.

At Web scale, the absolutely dominant vocabulary for mainstream search engines is schema.org. GoodRelations is a special case, since 99% of the GoodRelations vocabulary are now integrated in schema.org, so you do not have to choose between the two. In other words, schema.org is now a new namespace for using GoodRelations. Additional vocabularies may have relevance on the long tail and can typically be used in addition to schema.org with no negative effect. Once they will have gained sufficient popularity, search engines may care.

Now, you can use the same vocabulary in multiple syntaxes. For instance, you can publish schema.org in RDFa or Microdata or JSON/JSON-LD. The most appropriate syntax depends on the purpose and on the target applications of your data. In Web content, Microdata and RDFa should be equally well supported by search engines in theory. However, actual support varies.

As of now, I would recommend the following:

1. Microdata syntax for schema.org. RDFa works, but not all structural variants of the same data will be understood by search engines and you need to be a real expert to find out which ones work and which ones don’t.

2. RDFa for GoodRelations in the original namespace, since for historic reasons, search engines know well how to process it.

3. JSON-LD for schema.org in eMails and other upcoming scenarios, see also https://developers.google.com/gmail/actions/reference/formats/json-ld.

Microformats are a special case, since they combine syntax and vocabulary. For very simple data structures, this works well, and Microformats are widely understood by search engines. It is just my personal opinion, and I am sure advocates of Microformats will see things differently, but in the light of schema.org and generic syntaxes like Microdata, RDFa, and JSON-LD, Microformats will be limited to very basic usages, and likely fade out.

So in a nutshell, schema.org in Microdata is currently the most widely understood and recommended variant.

schema.org in RDFa and in particular JSON-LD may become more important in the future, but you will have to monitor closely to which degree search engines can actually process data in those syntaxes.

JSON-LD: Finally, Google Honors Invisible Data for SEO

For quite a while, I have been arguing that RDFa as a syntax for structured data in Web content is problematic when it comes to exposing more granular data than just a few property names. While many advocates of RDFa stressed that reusing the exact same visible elements for structured data markup, as in this example

<body> 
<div property="vcard:tel">+49-89-1234-0</div> 
</body>

was beneficial because it reduces redundancy, it also raises complexity for developers, since you violate the principle of “separation of concerns” – you have to align a given HTML tree structure with a given data structure, dictated by the vocabulary, like schema.org or GoodRelations.

As a consequence, I once developed and promoted the “RDFa in Snippets Style” approach, where the RDFa markup would reside in blocks of invisible <div> or <span> elements, like this:

<body> 
<!-- Content for humans --> 
<div>+49-89-1234-0</div> 
<!-- RDFa rich meta-data --> 
<div property="vcard:tel" content="+49-89-1234-0"/> 
</div> 
</body>

This has been a big success – most of the GoodRelations extensions for shop software, running on at least 20,000 Web shops globally, use that approach and get their content honored by Google.

Now, one caveat has always been that Google indicated that invisible markup, i.e. RDFa elements that do not reuse visible content, would not be honored. The likely rationale for that guideline was that

  1. invisible markup invites spammers that try to manipulate the search engine,
  2. a link to human-readable content allows to combine the structured data and the textual content for information extraction heuristics, and
  3. the data quality is likely higher for visible content (since humans will complain otherwise).

Now, in silence, RDFa in “Snippet Style” (and similar patterns in Microdata) have for long been accepted by Google, as long as other quality indicators for the site were positive. But there was always a doubt, which was bad, since the development effort for weaving in advanced data markup in RDFa or Microdata syntax into HTML templates in a form that combined visible content elements with data markup was, in my experience, 5 – 10 times higher as compared to using RDFa in “Snippet Style”.

The bigs news is that this uncertainty is going away, since Google now openly moves to accepting data markup in JSON-LD syntax not tied to visual elements.

Of course, this is just a first signal, but I personally think that in the future, we will see JSON-LD in script elements for all advanced data markup, and RDFa and Microdata only for the very simple use-cases.

That is a good sign towards a broader use of data markup for e-commerce, for sure.

Web Site Relaunch

Today, we finally released the complete update of our corporate Web site at http://www.heppresearch.com. While our main line of business is individual consulting with a selected number of clients, we thought it was high time to update our face to the public to the 2012 state of the art of Web development. After all, we claim to know how to do marketing in the next generation of the WWW, so we should show that we easily master the current one.

A key goal of the release was to support responsive design so that the page would work beautifully on any device, from a smartphone to my 30 inch screen in the office, and to migrate to HTML5.

I hope you like our new design as much as I do. Any feedback will be very much appreciated.

The new Hepp Research Web page

The new, responsive HTML5 Web design

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