Networking people love to talk about the network stack, like the 4-layer DoD model or the 7-layer OSI model, and web services boosters have picked up on that with their talk about the web services stack (an example from Judith Myerson at IBM , an example from David Orchard at BEA, and a bit of skepticism from Kendall Grant Clark) .

Should we be talking about a weblog stack? The web services stack almost always starts with HTTP rather than going all the way down into the lower-level networking protocols, so a similar weblog stack using RSS 2.0 would look something like this:

A diagram like this helps me to write an RSS library or aggregator, but does it leave me any more aware of how the blogsphere ticks? Not really, because not everything passes through this stack. For a non-full-text feed, for example, the headline and description show up this way, but then the main posting gets tome through a normal web HTTP+HTML route, totally independent of XML or RSS. Other kinds of communication bypass my proposed stack completely, like trackback and pingback, or even Technorati rankings for that matter.

Building a stack provides a cute technical model of one step in the weblog process, but it doesn’t explain how the whole thing works, much less why it works. In fact, human social products are almost always too messy to capture in simple trees or stacks. I faced exactly the same issue when I used to teach the history of the English language at university — technically, English is descended in a straight line from Old English, which is descended from proto-Germanic, which is descended from Indo-European. In reality, though, English borrowed an enormous amount of vocabulary and even syntax from languages like Latin, Greek, and French, which are not direct ancestors: imagine that you had your grandmother’s ears, but the nose of someone your mother happened to pass by on the sidewalk one day and a heart condition inherited from your father’s favourite 17th century Dutch painter, and you’ll see the problem.

Maybe the fact that weblog activities do not fit into a simple stack is not an unfortunate sign of a lack of intellectual rigour but the very reason for its success. Web services people, take note — you might want to try thinking less about new specifications and more about human behaviour.