Introduction to: RDFa by Juan Sequeda.
From the post:
Simply put, RDFa is another syntax for RDF. The interesting aspect of RDFa is that it is embedded in HTML. This means that you can state what things on your HTML page actually mean. For example, you can specify that a certain text is the title of a blog post or it’s the name of a product or it’s the price for a certain product. This is starting to be commonly known as “adding semantic markup”.
Historically, RDFa was specified only for XHTML. Currently, RDFa 1.1 is specified for XHTML and HTML5. Additionally, RDFa 1.1 works for any XML-based language such as SVG. Recently, RDFa Lite was introduced as “a small subset of RDFa consisting of a few attributes that may be applied to most simple to moderate structured data markup tasks.” It is important to note that RDFa is not the only way to add semantics to your webpages. Microdata and Microformats are other options, and I will discuss this later on. As a reminder, you can publish your data as Linked Data through RDFa. Inside your markup, you can link to other URIs or others can link to your HTML+RDFa webpages.
A bit later in the post the author discusses Jenni Tennison’s comparison of RDFa and microformats.
If you are fond of inline markup, which limits you to creating new documents or editing old ones, RDFa or microformats may be of interest.
On the other hand, if you think about transient nodes such as are described in A transient hypergraph-based model for data access, then you have to wonder why you are being limited to new documents or edited old ones?
One assumes that if your application can read a document, you have access to its contents. If you have access to its contents, then a part of that content, either its underlying representation or the content itself, can trigger the creation of a transient node or edge (or permanent ones).
As I will discuss in a post later today, RDF conflates the tasks of identification, assignment of semantics and reasoning (at least). Which may account for it doing all three poorly. (There are other explanations but I am trying to be generous.)