Top down being standards developed by committees (W*S, GML, CWS etc.), data sharing initiatives in the form of Spatial Data Infrastructures (SDI), and implementations built around protocols like SOAP. On the other end we have bottom-up approaches where de facto standards are created around iterated implementations (KML, GeoRSS, SpatiaLite etc.). Data sharing takes the form of indexed geodata that is directly Web accessible (e.g. Jason Birch’s work with Nanaimo). Protocols for implementation in the bottom-up category typically follow a RESTful philosophy.But, how do I find all this wonderful "bottom up" data? Here's a hint, it starts with "G"... Basically the "bottom up" folks have looked at the SDI publish-find-bind triangle and decided that "find" and "bind" are too much trouble. Someone else will have to deal with that. And fortunately (?), someone (starts with "G") has.
The rejoinder to my complaint is that the bottom up approach demonstrably works, while the SDI approach demonstrably doesn't. But that doesn't stop me from worrying about handing over a big part of the geo-webification program to a big, privately controlled, black box. One of Jason Birch's concerns about his elegant SEO-oriented approach to civic data publication was that the big black box was returning his data the "wrong way" (funneling certain address searches into the wrong place). We are back to hacking against a private black box API; it's Win32 all over again folks.
My geo-webby self loves that this stuff (mostly) "just works". My open-sourcey self worries that we are merrily affixing the golden handcuffs to ourselves. I, for one, am ambivalent about our new Googley masters.