From:Introducing ARC2 - ARC RDF Classes for PHP:

RDF researchers have been working hard on specifications and solutions for this rising Web of Data, and we see adoption in a variety of areas. One community, however, is still under-represented, and (not so) funnily, it’s the group of mainstream Web developers who kicked off data web trends like semantic markup, tagging, user-friendly information management, or mash-ups in the first place. Worse even, their great bootstrapping work towards a structured web is often not acknowledged and considered inferior to W3C-approved SemWeb specifications.

With ARC, we would like to reach out to the larger Web developer community, to enable the combination(!) of efforts like microformats with the utility of selected RDF solutions such as agile data storage, run-time model changes, standardized query interfaces, and mashup chaining.