<html>
<head>
<title>OpenACS WebDAV Support</title>
</head>
<body>
<h2>OpenACS WebDAV Support</h2>
<h3>Introduction</h3>
<p>This package implements a WebDAV interface to the OpenACS
Content Repository. In addition to generic access to content
items, there is a service-contract interface so packages can
define custom handlers for WebDAV methods for objects that belong
to that package.
</p>
<h3>How it Works</h3>
<p>OpenACS WebDAV Support requires the tDAV AOLserver module to
implement most of the WebDAV protocol. OpenACS WebDAV Support just
provides and interface between tDAV and the Content Repository
</p>
<p>Each content_type that requires a custom handler much implement
the <code>dav</code> service contract. Each content type should
implement the <code>dav</code> service contract with the implementation name the same as the content_type. This includes operations
for every WebDAV method. Some operations do not make sense for
certian object types. Specifically, content_items, which are
mapped to WebDAV resources, should not perform a MKCOL (make
collection) method. Likewise, a content_folder, or WebDAV
collection, should not allow a PUT method. In addition to the
<code>dav</code> service contract is a helper contract to allow
packages to set the initial content_type for new items created
through WebDAV. Each package should implement the
<code>dav_put_type</code> service contract with the implementation
named the same as the package key.</p>
<p>Each package instance that will allow WebDAV access should
register a package_id and folder_id for the root content_folder
that corresponds with the URI of the package's mount point using <code>oacs_dav::register_folder</code>.</p>
<h3>Dispatching Requests</h3>
<p>A preauth filter is registered for all WebDAV methods. This
calls oacs_dav::authorize which will set oacs_dav::conn user_id to
the OpenACS user_id or 0 is the request is not authenticated. This
filter also calls oacs_dav::setup_conn sets up the basic
information needed to authorize the request. If authorization
fails a 401 HTTP response is returned requesting authentication
information. If authorization is successful the filter returns
filter_ok and the tdav::filter* filter for the method is called.</p>
<p>The tdav::filter* commands setup global information for each
method that is independent of the storage type. After this filter
runs, the request is handled by the registered procedure for
OpenACS oacs_dav::handle_request.</p>
<p>oacs_dav::handle_request determines the package_id that should
handle the URI. This is based on the standard OpenACS site_node
Tcl API. After the package is found, the root folder for that
package is retreived from the dav_package_folder_map table. Using
the folder_id, and the URI of the request, the
<code>content_item__get_id</code> pl/sql(plpgsql) procedure is
called to find the item_id for the request. If no item_id is found
and the requested method is PUT, a new item should be created. If
the method is not PUT, a 404 error should be returned.
</p>
<p>oacs_dav::handle_request will call the service contract
implemenation for the content_type of the item. If the request is a
PUT, first the dav_put_type service contract for the package_key of
the request is called. For file-storage this returns
"file_storage_object" so items created by PUT are created as
file_storage_objects instead of generic content_revisions. </p>
<p>The service contract implementation for each operation must return
the response data in the format required by tDAV. The documentation
for the tdav::respond::* procedures named for each method describe
what is required.</p>