WebDAV学习笔记

• What is WebDAV?

Briefly: WebDAV stands for "Web-based Distributed Authoring and Versioning". It is a set of extensions to the HTTP protocol which allows users to collaboratively edit and manage files on remote web servers.

• what are the goals of WebDAV?
  • define the HTTP extensions necessary to enable distributed web authoring tools to be broadly interoperable, while supporting user needs
  • to support virtual enterprises, being the primary protocol supporting a wide range of collaborative applications
  • to leverage the success of HTTP in being a standard access layer for a wide range of storage repositories -- HTTP gave them read access, while DAV gives them write access
• What are the major features and benefits?
  • Locking (concurrency control): long-duration exclusive and shared write locks prevent the overwrite problem, where two or more collaborators write to the same resource without first merging changes. To achieve robust Internet-scale collaboration, where network connections may be disconnected arbitrarily, and for scalability, since each open connection consumes server resources, the duration of DAV locks is independent of any individual network connection.
  • Properties: XML properties provide storage for arbitrary metadata, such as a list of authors on Web resources. These properties can be efficiently set, deleted, and retrieved using the DAV protocol. DASL, the DAV Searching and Locating protocol, provides searches based on property values to locate Web resources.
  • Namespace manipulation: Since resources may need to be copied or moved as a Web site evolves, DAV supports copy and move operations. Collections, similar to file system directories, may be created and listed.
• Extensions to HTTP
  • over-write prevention
  • Properties
  • Namespace Management
  • Version Management :Supports the storage of important document revisions for later retrieval.Version management can also support collaboration by allowing two or more authors to work on the same document in parallel tracks. Automatic versioning records successive modifications to a resource made by versioning-unaware(“downlevel”) clients.
  • Addvanced Collections:Support for advanced resource collections that contain referential members, as well as collections ordered by the client. (In WebDAV, collections provide a mechanism for hierarchically organizing network resources.) Referential resources act like symbolic links in a file system, allowing the resource to be reused in multiple collections. They also allow the collection to contain non-HTTP resources.Ordered collections maintain a client-specified ordering of resources; they are useful, for example, in collections that contain human-ordered contents, such as the chapters of a book.
  • Access Control:Limits the access rights of a given authenticated principal on a given resource.WebDAV assumes that all WebDAV applications will support HTTP Digest Authentication, the cryptographic authentication scheme that is part of the HTTP 1.1 protocol.

 

•  over-write prevention:WebDAV provides an exclusive write lock, which guarantees that only the lock owner can overwrite a locked resource, and a  shared write lock, which allows a group of collaborators to work together on a resource.A WebDAV lock may have a scope of a single resource or a hierarchy of resources.
• Properties:All information published on the Web has many additional pieces of information associated with it,such as title, subject, creator, publisher, length, and creation date. This information about information (called properties within WebDAV, but also known as metadata) is particularly useful when searching for Web resources—by focusing a search on the value of a particular property (for example, the author), properties can be used to reduce the number of unrelated query results.