Chapter 5. WebDAV Modifications to HTTP

WebDAV reuses HTTP methods in authoring scenarios. The most frequently used methods are OPTIONS, GET, PUT, and DELETE. WebDAV doesn't do very much to change the behavior of these methods, because a WebDAV server ought to work well with an HTTP client that uses these methods. However, it's worthwhile reconsidering several HTTP requests in the context of the WebDAV data model and authoring scenarios. Here are the major issues considered:

• WebDAV URLs have more defined semantics.

• WebDAV has a couple of new ways to see what functionality is supported by the server or by individual resources.

• WebDAV adds new status and error bodies in responses to HTTP methods.

• Authoring scenarios require more careful use of ETags and similar mechanisms to see when resources change.

• Authoring scenarios introduce new performance concerns when using the HTTP methods.

This chapter and the three that follow cover all of the elements of RFC2518. This chapter introduces WebDAV URLs, feature discovery, and some new requirements that WebDAV imposes on HTTP methods. Chapter 6, WebDAV Hierarchy Operations, covers the operations used to manage WebDAV resources: MOVE, COPY, and MKCOL. Chapter 7, Property Operations, covers properties names, values, and how properties are changed and retrieved with PROPPATCH and PROPFIND. Chapter 8, Lock Operations, describes locking, LOCK, and UNLOCK.

The requirements in RFC2518 are generally clear, but interoperability testing has found some ambiguity or tricky parts. Deployed implementations like Web Folders have implemented the standard fairly well, but with some bugs or certain expectations. Thus, these four chapters include a number of recommendations that go beyond the standard, based on the experience of WebDAV implementors and participants in standards discussions in the last five years.