aaaaaaaaaahhhhhhhhh, I hate it when people spoil my yet-to-be-released RT :-(
I was holding an RT on "what is missing to the sitemap to *really* kick ass" waiting for 2.1 to be released final and one of the key points was to make it easier to write "webdavapps" in short "webapps" with DAV support.
Many people think of WebDAV as a protocol. I prefer to think of it as HTTP++. And web applications are made on top of HTTP, webdav applications should be made on top of HTTP++. It's as simple as that.
This looks indeed as a simple picture but (see below for more) it requires some good rethinking of our mental schemes after 10+ year of HTTP based development (gosh, a few days ago I downloaded the 10 years old version of Mosaic... ah, memories!). The HTTP world is mostly monodirectional, with just occasional bidirectional support which was, however, intended as a way of passing parameters rather than write data: POST being used actually as an alternative to GET makes that clear enough. Actually it's striking to see that PUT was there since the first versions and nobody cared that much, but I'll leave that for future ramblings. :-)
Now Cocoon, in its present incarnation, is heavily biased by the "read-only" syndrome, and this makes IMO very hard to enter the WebDAV world. I see two serious areas where WebDAV support needs careful (re)thinking of core Cocoon patterns:
1) URI space decoupling being unreversable: while this is a *major* feature of Cocoon (and something that might help immensely when applied to a DAV environment: views on WebDAV would really kick ass, imagine presenting your XML files as virtual OpenOffice .sxw that are assembled /disassembled on the fly), the drawback is that, in most cases, it's impossible to work your way from the pipeline result to the single pieces that make that result happen. Even the simplest XSLT transformation can't be reversely applied, so now there is no way to understand how an resource should be treated in a symmetric way when requested or uploaded. Oh yes, you can
<match pattern="*.xls">
<select type="request-method">
<when test="GET">
<generate src="{1}.xml"/>
<transform src="xml2poi.xls"/>
<serialize type="hssf"/>
</when>
<when test="PUT">
<generate type="xls2poi"/>
<transform src="poi2sourcewrite"/>
<transform type="sourcewrite"/>
<serialize type="dummyserializer"/>
</when>
[...]
</match>but this, apart from being ankward, doesn't work in general for all pipelines: think about aggregation at a very least.
2) direction: Cocoon is clearly designed for an "inside-out" type of flow in mind, while WebDAV is fully bidirectional. Design-wise it's difficult to adapt the G-T-S pattern to an incoming stream of data, when you're barely generating stuff (you're actually deserializing it) and, mostly, when you're not serializing anything but a simple response (think MKCOL, MOVE, DELETE and the like).
This said, I have no real solutions to that, but I'm very curious to learn more about your "extractor" concept. I think this is something needed, yes, but would that be enough?
webdav has been thought as a protocol for saving and retrieving files, but this is, again, another file-system injected syndrome of mod_dav. It
Though this makes it a tremendous tool too! The problem is that right now all the WebDAV implementations are "dumb" filesystems, where all you get is persistent storage. What I would love to see (and Cocoon would fit just perfectly) is the ability to build around the file system metaphore a whole set of components being able to react on the "filesystem" operation. In this case, a "save" (or "drag 'n drop") might mean an email sent to an administrator, or a workflow procedure being started: as easy as that, no client needed, just what we already got, networked shares and (maybe) a web browser: who needs a CMS client anymore then? Probably only CMS administrator, not users. Or (again) think about views/facets: being able to glue the Cocoon power to WebDAV might mean giving different content to each user. Graphics might see only images, and only in hi-rez: Cocoon will take care of making scaled down versions, while hiding them from the users. Possibilities are endless.
I would love to see cocoon becoming a framework that can glue together everything on the web, from stateless publishing from stateful webdav applications and yeah, why not, once you can do webdav applications you can do SOAP applications or XML-RPC applications, they are, more or less, all XMLoverHTTP stuff.
Oh, me too, believe me! This might be the Next Big Thing (hey... wait, are we ready to be 10 years ahead of the crowd? ;-)).
Now for the big question: should we leave this discussion for now, focusing on the upcoming release and take webdavification as one of the major challenges for the next generation (this alone might be a good reason for Cocoon 3.0 IMHO), or shoud we have some more fun on the topic here and now?
Ciao,
-- Gianugo Rabellino Pro-netics s.r.l. - http://www.pro-netics.com Orixo, the XML business alliance - http://www.orixo.com (Now blogging at: http://blogs.cocoondev.org/gianugo/)
