The popularity of widgets these days has brought to attention the need for interoperability, i.e. for widgets developed for one site or platform to be able to run in other sites and widgets developed by different people to be able to work with each other.

So much so that I know of at least 3 somewhat competing specifications for widgets.

There's the gadget portion of the OpenSocial specs which was adopted from the Google Gadgets work. Then there's OpenAjax which is more broadly focused on Ajax interoperability but has a lot of pieces geared towards widget interoperability.

And finally there's the W3C's Widgets 1.0 Family of Specifications. Based on a preliminary analysis, the OpenAjax specs appear to be the most comprehensive for widget interoperability issues but OpenSocial seems to have gained more adoption.

The W3C work appears to be moving very slowly (no surprise) and it's unclear to me how much adoption they have. Right now my preference is the OpenAjax specs based on how comprehensive it is but admittedly I have not done a thorough analysis and comparison of the three. Plus, a spec that is too comprehensive may not always be a good thing, e.g. tends to be more complex and may be trying to standardize more than what's necessary.

Stay tuned, I'll post a more thorough analysis once I've had more time to parse through each of them in more detail.