Greetings.
[I'm experimenting with WADL for the first time, so apologies if I'm
misunderstanding something]
In the WADL spec, the status of an HTTP transaction is modelled in the
<representation> element. This seems eccentric, and I'm wondering if
I'm missing some constraint.
There was a brief discussion of this in February (I see from the
archive <
https://wadl.dev.java.net/servlets/ReadMsg?
list=users&msgNo=59>), but it was inconclusive, and ended with Marc
Hadley saying
> I suppose allowing multiple sibling Response elements and having the
> status on those might be more amenable to what you are trying to do.
Though I'm not sure whether this was a suggestion, or thinking-aloud
about a fix. If the latter, then yes, I think that the following
would make more conceptual and practical sense.
<response status='200'>
<representation mediaType='text/html'>
....
The problem is that the HTTP status in the response, and the
representation enclosed in the response, are very distinct, so that
conceptually they have no business being coupled together so closely
as they are in the current model.
RFC2616 defines a 'representation' as
> An entity included with a response that is subject to content
> negotiation, as described in section 12. There may exist
> multiple
> representations associated with a particular response status.
That indicates that the representation is _part_ of a response, and
the status is a separate part of the response, and not part of the
representation.
More practically, the current WADL model means that if I have two
resources, say /A and /B, which both return text/html, but a POST to /
A returns HTML with a 201 status, and a GET to /B returns HTML with a
200 status, I can't do
<resource name="A">
<method name='POST'>
<representation href='#html'/>
</method>
</resource>
<resource name="B">
<method name='GET'>
<representation href='#html'/>
</method>
</resource>
...
<representation id='html' mediaType='text/html'>
<doc>A full discussion of HTML, with references and whatnot</doc>
</representation>
It wouldn't do to say
<representation id='html' mediaType='text/html' status='200,201'/>
since that doesn't let me say that only /A responds 201 and only /B
responds 200. The alternative is to have separate <representation>
elements within the two <resource> elements, but that would mean I'd
have to either duplicate or omit the possibly elaborate documentation
of the #html response representation.
For the sake of concreteness, can I therefore suggest the following as
alterations to the WADL schema
method =
element wadl:method {
(
(
attribute href { xsd:anyURI }
) | (
doc*,
request?,
response*, ### instead of response?
attribute id { xsd:token }?,
attribute name {
"DELETE" | "GET" | "HEAD" | "POST" | "PUT" | xsd:token
}
)
),
foreign-element,
foreign-attribute
}
response =
attribute status { xsd:int }, ### addition
element wadl:response { <blah> }
...and omit attribute 'status' from representation_type.
Best wishes,
Norman
--
Norman Gray : http://nxg.me.uk
Physics and Astronomy, University of Leicester