Marc Andreessen wrote an interesting blog post back in September entitled, "The three kinds of platforms you meet on the internet". In it he makes the following assertion, taken verbatim from the blog post:
  • A Level 1 platform's apps run elsewhere, and call into the platform via a web services API to draw on data and services -- this is how Flickr does it.
  • A Level 2 platform's apps run elsewhere, but inject functionality into the platform via a plug-in API -- this is how Facebook does it. Most likely, a Level 2 platform's apps also call into the platform via a web services API to draw on data and services.
  • A Level 3 platform's apps run inside the platform itself -- the platform provides the "runtime environment" within which the app's code runs.
And as Jon Udell points out in, "The fourth platform", there's a level 4 platform where, "the cloud of storage and computation is partly centralized in a handful of intergalactic clusters, and partly distributed across a network of humble peers".

Currently Compendium Blogware is a "Level 1" platform. That is, via a services API (JSON in our case), you can do things like:
  • Create and Edit Posts
  • Find Posts
  • Fetch announcements
  • etc
This means that with a level 1 platform, assuming you expose all functionality via a services API, someone can build an identical offering to the one you have built yourself. It becomes obvious however that users may want to extend the default application with their own functionality, and thus providing a plug-in API becomes necessary. Now you're a "level 2" platform.

Now, a clear advantage to having your SAAS (Software As A Service) provider host your application, as a level 3 platform does, is that you don't bear the burden of hosting and your uptime theoretically improves. The downside is that now the SAAS provider owns your application (in the sense that it's non-portable to another platform).

The question that deserves asking is, how useful is a computing platform for blogging? It seems obvious that just from an availability perspective, provider hosted applications are a good thing. However, the time and resources required to build a "level 3" platform are significantly more then for a "level 1" platform. The availability argument may win over in the long run however. Given how few level 2 and level 3 sites are out there, it will be interesting in 2008 to see how the landscape changes.