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[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: SOAP and the Web
 Francis Norton wrote: > >... > I know I have a bit of a blind-spot here. What is the canonical example > of a "resource" v. a "representation"? Say I wanted to look up trains > from London to North Berwick - is the URL of the query a representation > of the timetable resource? The timetable is a resource. A URL is never a representation: the representation is the stuff that gets sent across the wire: the XML or XHTML or whatever. It is what you GET and PUT. Here's the radical bit: ideally there would be *no* query in this system. Let's say the XML was organized like this: <routes> <route from="http://train.com/cities/London" to="http://trains.com/cities/NorthBerwick" href="http://trains.com/routes/LondonToNorthBerwick"/> </routes> Then you have the document: http://trains.com/routes/LondonToNorthBerwick It has: <times> <time>ISODATE1</time> <time>ISODATE2</time> <time>ISODATE3</time> <time>ISODATE4</time> <time>ISODATE5</time> </times> Now you get into this service through the "routes" document above, follow the hyperlink to the "ondonToNorthBerwick" document and find the information you need. You've never done a query and you've never had to send complex XML. When you do it this way: 1. the client's access to the data is not mediated by any API or messaging interface. This is very much in the XML spirit of "give me the data and I (the client) will figure out what to do with it. 2. you cannot generate a "bad query" by trying to get from London, Ontario to North Berwick, Scotland (nor North Berwick Maine to London, England!). If there is no link for that route then you can't get there. 3. the client can discover routes, rather than merely generate them and test whether they exist or not. For instance it could say: "hmmm. I notice a route from London to Glasgow and Glasgow to North Berwick. Maybe this is also interesting to my user." 4. the standardization of the "routes" format and the "times" format can actually be fairly disconnected. For instance we might use the same "times" format for airlines and trains but the "routes" format might be different. Or else we could use XML extensibility features to share both but have different details on both. 5. the server can easily serve these as either dynamic OR static documents. The performance advantages to the latter should be obvious. >... That seems simple enough, but what is the > representation that I send - one representation of the train route from > London to North Berwick, or a combination of representations for the > locations of London and North Berwick? It's like asking how you model objects in an OO systems. I guess I would tend towards breaking things apart rather than combining them but that's just a very rough rule of thumb. But note that the question is really how you break out the *resources*. Representations just represent resources on the wire. > I like the way that W3C specs come with "this version" and "latest > version" links at the top, and I find it frustrasting that I can't refer > to resources in Visual SourceSafe in the same way, so I think I'm making > progress... Yep, using hyperlinks like that is very resty. Visual SourceSafe probably has an "API" that allows you to access older versions through code. That's a very "SOAP-y" way to look at it. >.... > >XForms *does* have GET support. > > > Can XForms understand GET or POST Web Services described in WSDL? I > imagine WSDL is a bit short on form layout details, but does XForms have > helpful deaults? XForms does not know anything about WSDL. After all the former is a W3C specification and the latter has only just begun its standardization process. And anyhow, they are kind of parallel specifications. WSDL is used to map the interface to a web site into an interface suitable for programmers. XForms is used to map it into an interface suitable for humans. There wouldn't be that much in common between them other than the XML Schema. Paul Prescod 
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