WebDAV是HTTP的一个扩展，作为一个文件共享的标准不断发展。当今的操作系统变得极端的web化，许多内置了对装配WebDAV服务器导出的“共享”的支持。
如果你使用Apache/mod_dav_svn作为你的Subversion网络服务器，某种程度上，你也是在运行一个WebDAV服务器。这个附录提供了这种协议一些背景知识，Subversion如何使用它，Subversion如何和认识WebDAV的软件交互工作。
DAV的意思是“Distributed Authoring and Versioning”。RFC 2518为HTTP 1.1定义了一组概念和附加扩展方法来把web变成一个更加普遍的读/写媒体，基本思想是一个WebDAV兼容的web服务器可以像普通的文件服务器一样工作；客户端可以通过HTTP装配类似于NFS或SMB的WebDAV共享文件夹。
悲惨的是，RFC规范并没有提供任何版本控制模型。基本的DAV客户端和服务器只是假定每个文件或目录只有一个版本存在，可以重复的覆盖。
因为RFC 2518漏下了版本概念，几年之后，另一个委员会留下来负责撰写RFC 3253来添加WebDAV的版本化，也就是“DeltaV”。WebDAV/DeltaV客户端和服务器经常叫做“DeltaV”客户端和服务器，因为DeltaV暗含了基本的WebDAV。
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 well.
When Subversion was still in its design phase, it seemed like a great idea to use Apache as a 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.
这是什么意思呢？
First, the Subversion client is not a fully-implemented
DeltaV client. It needs certain types of things from the server
that DeltaV itself cannot provide, and thus is largely dependent
on a number of Subversion-specific
HTTP REPORT requests that
only mod_dav_svn understands.
Second, mod_dav_svn is not a fully-realized 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.