There's been a number of attempts at changing the current standards for metadata, the most recent being Common Tag.What I find different about this one is that Yahoo are already supporting it, so with support from one of the big league search engines (relatively speaking) it is quite possible that this standard could become mainstream in the next couple of years. What this project draws upon is that there are many tags you could use for your content to identify it.
in the absence of a common tagging format, the benefits of tagging have been limited
Individual things like New York City are often represented by multiple tags (like “nyc”, “new_york_city”, and “newyork”), making it difficult to organize related content; and it isn’t always clear what a particular tag represents—does the tag “jaguar” represent the animal, the car company, or the operating system?
To get around this problem their idea is to have a library of "common" tags which have stored with them a series of alternative tags for that common tag (as described in the quote), and then when searching for any of those tags on Yahoo it will understand what related tags there are and use those also.
Actually using this needs the addition of an XML namespace to elements on your page so that you can tag pages at element level.
<div xmlns:ctag="http://commontag.org/ns#"
about="#second" rel="ctag:tagged">
<span typeof="ctag:Tag"
rel="ctag:means" resource="http://dbpedia.org/resource/Luke_Skywalker"/>
</div>So as you can see they don't actually utilise the meta tag at all - it is added to the actual content. This same method can also be applied to objects (for Flash objects for example) and to images meaning this could also be used in specific image or multimedia searches.
I've not started using this myself yet, I think it's something to keep an eye on as in some cases it almost feels like it's encroaching on microformats territory - I think it would work out better if the two somehow merged however this would require the current system for Common Tag to be changed which is unlikely to happen (at least for any serious change).
