The original WebDAV standard has been widely successful.
Every modern computer operating system has a general WebDAV
client built-in (details to follow), and a number of popular
standalone applications are also able to speak WebDAV —
Microsoft Office, Dreamweaver, and Photoshop to name a few. On
the server end, the Apache webserver has been able to provide
WebDAV services since 1998 and is considered the de-facto
open-source standard. There are several other commercial WebDAV
servers available, including Microsoft's own IIS.
DeltaV, unfortunately, has not been so successful. It's
very difficult to find any DeltaV clients or servers. The few
that do exist are relatively unknown commercial products, and
thus it's very difficult to test interoperability. It's not
entirely clear as to why DeltaV has remained stagnant. Some
argue that the specification is just too complex, others argue
that while WebDAV's features have mass appeal (even the least
technical users appreciate network file-sharing), version
control features aren't interesting or necessary for most users.
Finally, some have argued that DeltaV remains unpopular because
there's still no open-source server product which implements
it.
When Subversion was still in its design phase, it seemed
like a great idea to use Apache httpd as the main network
server. It already had a module to provide WebDAV services.
DeltaV was a relatively new specification. The hope was that
the Subversion server module (mod_dav_svn) would eventually
evolve into an open-source DeltaV reference implementation.
Unfortunately, DeltaV has a very specific versioning model that
doesn't quite line up with Subversion's model. Some concepts
were mappable, others were not.
The upshot is that
-
The Subversion client is not a fully-implemented DeltaV
client.
The client needs certain things from the server that
DeltaV cannot provide, and thus is largely dependent on a
number of Subversion-specific REPORT
requests that only mod_dav_svn understands.
-
mod_dav_svn is not a fully-implemented DeltaV server.
Many portions of the DeltaV specification were irrelevant to
Subversion, and thus left unimplemented.
There is still some debate in the developer community as to
whether or not it's worthwhile to remedy either of these
situations. It's fairly unrealistic to change Subversion's
design to match DeltaV, so there's probably no way the client
can ever learn to get everything it needs from a general DeltaV
server. On the other hand,
mod_dav_svn
could
be further developed to
implement all of DeltaV, but it's hard to find motivation to do
so—there are almost no DeltaV clients to interoperate
with.
