Microformats vs. RDF: How Microformats Relate to the Semantic Web

Microformats are a wildly popular set of formats for embedding metadata within normal XHTML. The primary advantage Microformats offer over RDF (including its embedded serializations) is that you can embed metadata directly in the XHTML, reducing the amount of markup you need to write (e.g. you don't have to write XHTML and additional RDF). Many people have contended that Microformats are a possible replacement for RDF, however Microformats were not designed to cover the same scope as RDF was. While both Microformats and RDF make it possible to store data about data, they simply do not work to solve the same set of problems.A quick comparison

I don't blame the Microformats people for this confusion over what Microformats are or are not. Rather, I blame the sensationalists and know-nots that tend to jump on any new standard, format, or design pattern. Directly on the Microformats about page you are told what Microformats are and are not.

What Microformats were not intended to be:

* A new language
* Infinitely extensible and open-ended
* An attempt to get everyone to change their behavior and rewrite their tools
* A whole new approach that throws away what already works today
* A panacea for all taxonomies, ontologies, and other such abstractions
* Defining the whole world, or even just boiling the ocean
* Any of the above

There you have it, clearly stated and all. I would guess that most of the arguments made by pro-RDF people are extinguished after reading that unordered list. However some people still believe that we can create the Semantic Web with Microformats.

What RDF allows (and Microformats lacks):

* Resources are represented as URIs, allowing you to access metadata remotely
* Infinitely extensible and open-ended design
* A powerful Ontology language (OWL) that is built upon it
* The ability to utilize, share, and extend any number of vocabularies
* No reliance on pre-defined "formats" (i.e. not limited by the types of data that can be encoded)

As you can see there are a few things we can do with RDF that cannot be done with Microformats. The Semantic Web relies on the things I've listed above. These are the clear-cut reasons why Microformats will not be part of the W3C's Semantic Web vision.
Persisting the data within Microformats

Another issue I've thought about is how we are to persist the data we glean from Microformats. How do you usefully store Microformat metadata (beyond leaving it in its XHTML form)? The information stored in Microformats eventually comes out in triple form, one way or the other. Take a look at this example:

home:
+1.415.555.1212

What information can be gleaned from this example? Well, the home telephone number (of an unknown person or entity, in this example) is +1.415.555.1212. In the end we are still getting the subject-predicate-object form. In this case the subject would be the owner of that number, the predicate would be "home," and the object is the telephone number itself.

So really, we will likely require triple storage for either RDF or Microformats. In all honesty, I don't know of any Microformat-stores. If you know of some, I would like to know if they are any different from a normal triple-store.

Microformats have a place and a purpose

At this point I'd like to say that Microformats do have a number of qualities that RDF (although not necessarily all serializations) does not accommodate for, at least not in the same way:

* Designed for humans first, machines second
* Modularity / embeddability
* Enables and encourages decentralized development, content, services
* A design principles for formats
* Adapted to current behaviors and usage patterns
* Highly correlated with semantic XHTML

I've stated before that I believe Microformats will help bring about the Semantic Web by introducing "metadata sprinkling" (the act of including metadata in otherwise "normal" data) to more people. They allow for simple metadata embeddability and do not affect how an XHTML document validates. This is the kind of approach that will help normal users come closer to understanding the Semantic Web vision.
Conclusions

To me, Microformats are to RDF as HTML 5 is to XHTML; on the surface they both appear to be a solution to the same problem, but the former misses the point as to why the latter was created. On the very same about page I cited earlier there is a bullet point that suggests that Microformats will be part of the semantic web (note the lowercase letters, implying a semantic web, not the one envisioned by the W3C). I find that all competing Semantic Web development paths fall short of creating an entirely linked Semantic Web. The kind of Semantic Web that gives us a platform to stand on above the Web document layer. Microformats have their place, just not as a replacement to RDF.