The idea of Cascading RSS (or aggregation aggregation) is so obvious that it has probably already been blogged to death or even implemented by well-known web sites; unfortunately, my short attention span ran out before I think up the right search words for Google, so I’ll pretend that it’s my own, original idea for now. We use RSS or Atom to tell people when a web resource has changed, but that can still involve polling dozens or hundreds of RSS files frequently. With only a few tiny tweaks, we could also use master RSS files to tell us when other RSS files have changed, cutting the polling by (potentially) orders of magnitude.
I can think of a couple of places where this approach could allow RSS into places where it hasn’t been able to go yet:
A very enlightened company might realize that RSS gives it an excellent way to manage information from all of its divisions, branches, subsidiaries, partners, and so on. Everyone simply puts data (sales figures, inventory, projects, and so on) on the company intranet as XML data files (presumably with appropriate authentication and authorization requirements) and then uses RSS to announce when new information is available or old information has changed. If division X needs to monitor inventory data from division Y, it polls division Y’s inventory RSS file every 5 minutes to see if there’s anything new.
The problem is that the network will get messy if the company ends up with thousands of RSS files, and everyone is polling everyone else’s every 5 minutes, especially if some of them are on old, slow servers. To simplify things (and speed them up), the company could have one fast server that polls all the RSS files in the company and then produces its own RSS file with the most recent change dates for each one. Now, everyone can poll only that central server, but the divisions still own their own data. Of course, it would be possible to build this up in several cascading layers to avoid one RSS file with 1,000 entries.
Sooner or later, we’ll have personal RSS for reporting information like credit card and bank transactions, as Tim Bray predicted almost two years ago. One of the biggest problems here, though, is that people might be reluctant to give personal passwords to online aggregators like Bloglines. People might, however, allow online aggregators to request the last-modified time of their credit card or bank feeds, and they could use these to build cascading RSS files, allowing users to reduce the amount of polling they have to do from home or on the road.
In other words, both advantages have to do with getting RSS into the business world (either B2B or B2C), not with improving the current blogosphere. I’ll look forward to finding out who has thought about this idea in more detail, or even implemented it.