- From: Geoffrey M. Clemm <geoffrey.clemm@rational.com>
- Date: Sun, 4 Feb 2001 15:42:15 -0500 (EST)
- To: ietf-dav-versioning@w3.org
Rather than define a variant of the WebDAV XML, and negotiate for different variant of the XML with the Content-Type header, wouldn't it be much simpler just to allow property tags to be empty in the DTD? Cheers, Geoff Date: Sun, 04 Feb 2001 02:56:27 +0000 From: "James J. Hunt" <jjh@allerton.de> Dear Colleagues, After much thought, we have finally devised a way to provide for XML validation in DeltaV without breaking existing WebDAV clients. There are only two points where the DTD given in WebDAV is not validatable:=20 property tags occur both as empty-element tags and as begin/end tag pairs, and though the DTD is named webdav-1.0, it gives no definition for that tag. Two small changes would make the DTD usable. The problem is that to do this, an incompatibility would be introduced between current implementations and ones based on the new DTD. The solution to this problem is to define a full validatable DTD for DeltaV including the modifications to webdav,then provide for two modes of operation. Since a server can only react to a client request, it can send a response in the correct mode based on the HTTP header sent by the client. A server MUST send an old style WebDAV response if the option "valid=3Dtrue" is not listed in the Content-Type header entry. = However, if the media type contains "valid=3Dtrue" as follows, the server MUST = send valid XML: Content-Type: application/xml; charset=3D"utf-8"; valid=3Dtrue The presence of the valid=3Dtrue option means that the XML being sent = is valid, but it does not mean that the receiver must check that validity. = Validation is done at the receivers discretion. Note, that application is used here instead of text. Though WebDAV specifies either text or application, text is not really appropriate, because text is meant for documents designed for display to a user. Here, XML is intended for information exchange between programs. A client must ask the server if it supports valid XML. If a server returns a DAV responseheader containing version-control, then the = server MUST support valid XML. The client can then send the appropriate XML message. Non valid XML messages are limited to those used by WebDAV. These rules insure that all old clients will work with new version-control servers and all new client will work with old WebDAV servers. Since the changes to the WebDAV part of the protocol are small, supporting both forms of WebDAV messages is not much of a burden on either clients or servers. The use of valid XML is then an extension to WebDAV, that is introduced by DeltaV. WebDAV could use the same method to add valid-xml as a general option in its next draft. Sincerely, James J. Hunt J=FCrgen Reuter
Received on Sunday, 4 February 2001 15:43:14 UTC