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Linking to SOAP-exposed resources
Since the REST/RPC/SOAP discussion flared up again, I've been looking for a single clear statement about what kind of problem may exist, and what to do about it. I found it in Paul Prescod's Google's Gaffe:
The point that has not yet filtered through to the mainstream of web services implementors is that linking is just as important for machine-to-machine applications as it is for human-facing applications. If it is impossible to link to SOAP-exposed resources, then they are less powerful and useful than HTTP-exposed ones. Until SOAP has an addressing mechanism as rich as HTTP URIs, SOAP is less, rather than more powerful than HTTP. A hugely important class of web services is addressable by URI, and accessible to GET. We call these things web pages. The fact that such pages can be consumed by human-operated browsers and machine-operated scripts in the same way was, and remains, a great thing. As some pages evolve into services intended mainly for programmatic use, XML becomes a natural representation format. This need not undermine the value of the URL-line which, as I've pointed out, remains an incredibly vital style of access.
In practice, though, I don't find that SOAP undermines the URL-line. Toolkits seem perfectly happy to let me turn service names, method names, and parameters into URLs. I have here, for example, both Visual Studio.NET and GLUE. If I write a SOAP service called StockQuote in either of these, with a method called getQuote, then in addition to the SOAP/RPC interface I can automatically use:
http://host/StockQuote/getQuote?sym=VRSN
or:
http://host/StockQuote.asmx/getQuote?sym=VRSN
Should Google have done something like this? Absolutely. I miss being able to type http://google.com/xml?q=roy+fielding. As I pointed out in a essay on monetizing web services, this was possible a few months ago. Arguably it still should be. But that's just a business decision Google has made. In practice, given the restrictions placed on the Google API, the regular web-friendly HTTP GET remains the preferred way to link to the infinite space of Google queries, as people do every day.
So, SOAP toolkits already support a RESTful mode for GET-style (though not for POST-style) operations. Since GET-style reads are what both people and machines mainly use the Web to do, I'd say we're in pretty good shape.
PS: The top Google result for "restful soap" -- ahead of a bunch of W3C mailing list postings -- is an ad for a restful soap full of aromatic fragrance. The name of this restful soap? Desert Storm. Go figure.
2:04:18 PM 
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