Rethinking GSDI Architecture

Ed Parsons and Chris Holmes were at the GSDI-10 conference and have each written posts about "GeoWebs" and "Global Spatial Data Infrastructures" that touch one of my favorite topics: architecture. Ed says that it is time for grand data sharing designs to yield to an evolutionary approach:

So we need to move away from the "Grand Design" approach and build SDI's organically and simply, perhaps making use of the new Global infrastructures that companies like Google and Microsoft have made available to bootstrap the technology, and deliver faster benefits and to make the case for more in depth infrastructures at a later date.

It's great that the GSDI community is hearing this. Yes, Ed is pitching Google's services as he pitches the Web, but I think it's still an honest argument for the Web. The Web works: not only for Google, but for thousands of other business, governmental, and non-profit enterprises, and for billions of users.

I only need to make one little correction or addendum to these paragraphs in Ed's post:

The Grand Design approach does introduce an additional issue which is technology related, many of the current SDI projects are planned to deliver over decades, with technological developments continuing to move rapidly, it is difficult to plan to implement using a technology which will be obsolete years before the infrastructure goes live.., as it is today the best available standards as drafted by OGC are moving from basic http interfaces to the more web services friendly SOAP based interfaces, while the leading edge is looking to REST based interfaces.

Mostly right. When we say "REST", we mean protocols based on the HTTP application protocol, and the architecture that makes the Web a success. REST is not a radical prescription at all. When you consider that REST won the distributed systems architecture war, to take the losing approach forward seems much more radical.

Chris Holmes's presentation is focused on social change, top-down yielding to bottom-up, but when he writes (on slide 19) that GSDI should

build on what's out there, on successful architectures of participation.

there are to me clear technical implications: The Web has an "architecture of participation", and its architectural style is named Representational State Transfer, or REST. I don't fault Chris at all for not directly pointing out that the OGC architecture is misaligned with the architecture of the Web: it's a distraction from his social message and possibly demoralizing to GIS data managers. But I don't think you can for very long dodge the issue that a "GeoWeb" really demands a RESTful Web-like architecture, and something like HTML. Hypertext, not GetCapabilities() and GetData().

Comments

Re: Rethinking GSDI Architecture

Author: Ed Parsons

Sean, I think we are in agreement I did not mean to suggest that REST was radical, it is just some way away from where we are now with the earlier http based OGC interfaces. In terms of searching for Geospatial content a RESTful approach makes life much easier.. ed

Re: Rethinking GSDI Architecture

Author: Sean

And I'm glad we're in agreement. It's just that I didn't think it was clear enough that the leading edge (REST) uses good old reliable HTTP and is arguably the more conservative approach to distributed systems.

Re: Rethinking GSDI Architecture

Author: Allan Doyle

Conservative architecture is something that evolves from what people are familiar with, and that is not necessarily the same as something that is elegant, simple, and robust. Computing architectures "matured" in the days of IDLs (interface definition languages) and compiled stubs that when instantiated provided systems that were distributed but still tightly coupled. Sun RPC begat the Distributed Computing Environment which begat CORBA. Microsoft COM begat DCOM which begat OLE COM (or was it COM OLE, and which came first anyway? it's all a blur). Then while the radicals were looking at REST, the conservatives began to build WS-*. From a business and management control perspective, REST is radical. It removes all the ivory-tower layers that have been accreting for what must be close to two decades. So no matter how conservative it may seem to those who understand REST, it remains something mysterious to a large segment of the computing industry. Similarly, SDIs have grown up around the notion of control, this time in terms of metadata, framework data, data accuracy standards, and on and on. The radical thought here is that maybe you don't have to have all of that at once to start doing something useful. The good qualities of SDI will eventually remain, but largely hidden from the view of most of the beneficiaries of all the geospatial functionality that has been able to push its way into the forefront of late.

Re: Rethinking GSDI Architecture

Author: Allan Doyle

Or, to be more succinct: REST is the radical thought is that you can have your apps be (part of) the web instead of just having them use the web. And therein lies the "architecture of participation".

Re: Rethinking GSDI Architecture

Author: Sean

Allan, I appreciate the reminder that the Web still seems new and maybe a little immature to the old guard. I admit that I take it for granted.