Re: Is it a good idea to make your WADL available?

Paul Downey writes:

> On 5 Sep 2006, at 20:35, Mark Baker wrote:
> 
> >
> > +1, on all counts.
> >
> > The frustrating thing here from my POV, is that WADL is very nearly a
> > forms language; consumable at runtime in order to direct a hypermedia
> > application.  It just needs a few tweaks, as well as to make clear
> > what's authoritative and what isn't.
> 
> In many ways both WADL and 'Forms' are the same - they're just
> Web pages at the end of a URI describing what you might like
> to send to another URI. 

The TAG draft finding on metadata in URIs takes that same view of HTML 
forms, at least in the example at [1] 

I think it's the temporal nature which is the issue here - how long
can you leave between grabbing a WADL (or a HTML form) and then
making GET/POST requests based upon that information?

> I think it's the temporal nature which is the issue here - how long
> can you leave between grabbing a WADL (or a HTML form) and then
> making GET/POST requests based upon that information?

Well, inosfar as cool URI's don't change [2,3], forever. Once that form 
goes out from the authority documenting its intended use of a set of URIs, 
then in a well run system we can assume that those URIs will continue to 
to represent the same resources in perpetuity.  Insofar as the form or 
WADL contains hints about the representation, those may become stale, but 
we've already said earlier that the representations returned are 
authoritative.  It should not be surprising that hints can become stale in 
a dynamic system.

> In many ways the 'authoritative' nature of metadata is an orthogonal
> issue given there are similar issues for all metadata, including 
> Content-type.  It's tempting to specify a policy for a WADL or a 
> form 'yes, we're committed to supporting this' but then that's just 
> more metadata about, um, metadata.

The draft TAG finding takes the view that forms and similar documentation 
provided by the resource authority are themselves authoritative.So, if I 
source from example.org an HTML form that says:  "Type in a city name and 
push the button to get the latest National Weather Service data for that 
city", and if the form implements the obvious templated URI to generate a 
family of URIs using query strings, and crucially if those URIs are 
administered by the same authority (example.org), which we can tell from 
the DNS addresses, then I have made an authoritative statement about the 
purpose of the whole family of URIS.  If those are cool URIs, I've 
committed that they will refer to the weather forever.

Converseley, if you send out an HTML form that builds URIs in my domain, 
the story is different:  you can't commit me as a URI assigment authority, 
unless I have somehow delegated that capability to you.  So, it depends 
where the form or WADL comes from, IMO.

Noah

[1] http://www.w3.org/2001/tag/doc/metaDataInURI-31.html#forms
[2] http://www.w3.org/TR/webarch/#URI-persistence
[3] http://www.w3.org/Provider/Style/URI.html

--------------------------------------
Noah Mendelsohn 
IBM Corporation
One Rogers Street
Cambridge, MA 02142
1-617-693-4036
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Received on Wednesday, 6 September 2006 13:04:36 UTC