Dave's plan to rethink RSS has potential. I've always liked the simple concept of title, link, description (text) and categories. Making a RESTful, JSON API would be great. I've been dabbling towards that with a project I've been working on that started with Zlides.com and OPML combined with JQuery Mobile. So I've been giving this some thought.
Dave likes Twitter. The Twitter API is proven itself and lessons have been learned. Lots of people know it. So my comments below reflect my usage of the Twitter API, particularly the search API.

1. JSONP. The ReallySimple API should support JSONP. The primary benefit is cross-domain support so I can write browers apps hosted on any site and use the reallysimple.org api. This would make it much easier to write mobile apps using JavaScript, HTML5 and CSS. For an example, look at the Twitter Search wiki and how they support JSONP. Also look a jquery's support for JSONP.
2. Categories. RSS has always supported categories and I was rather suprised not to see them in the API. Much of web 2.0 worked leveraged categoris and I think it is an important addition.
3. RESTful. Several people have commented on using the RESTful verbs. I certainly support that for GET and POST but since DELETE and PUT are harder to implement there should be more discussion of that.
   
4. Extending Really Simple. RSS supports namespaces and there should be someway to extend the Really Simple api. Steve Moyer commented about having extra fields like _rev in the API. In my view, extra fields would be fine but probably ignored by most clients. It would probably be better to suppress them, but in some implementations there are cases were the extra fields would add a feature. More discussion needed.
5. getPost. Given an idPost, I would want to get the JSON for just that post. The id could be the permalink. And perhaps, maybe I supply a link and get back an array of posts which could be all of the comments made to a post.
6. Enclosure. Very encouraged to see it supported. Important in this world of videos, photo blogs and other media files.
7. OAuth. Twitter and others have moved away from basic authentication for a reason. I would suggest supporting OAuth like twitter.
   
8. No date. The format of title, description and link is so powerful that it applies to more than just reverse chronological blogs. The web content management system (CMS) that I wrote had RSS feeds as its foundation. [I'll have to add the ReallySimple API to it.]  And see example of Wikipedia below. However, I would think that this might be an expected field. Or perhaps it is better to ignore it for right now given the discussion that will start about date format.
   

ReallySimple maps to ReallySimple HTML pages as well. It supports title, link, description and hopefully category. This also maps directly to standard Web 1.0 content web pages where one HTML page contains content on a subject. For example, this Wikipedia page on Daly Languages has a title and obviously a link. The content is inside the body tag, less the navigation, footers and banners. Categories in the metadata and displayed on the page. So I should be able to take the primary content of this page and easily put it into a JSON message using the ReallySimple fields. Lots of features could be built off having an entire page in JSON.

I look forward to using the ReallySimple API with mobile apps and Couchdb apps.

Cross posted from: http://raydaly.posterous.com/really-simple-api-first-comments