Understanding versioning（from arcgis desktop help）翻译

Versioning allows multiple users to edit the same data in an ArcSDE geodatabase without applying locks or duplicating data. A version can represent an engineering design, a construction job, or any other type of transaction. The basic concepts of versions are as follows:

What a version is

• A version represents a snapshot in time of the entire geodatabase. It contains all the datasets in the geodatabase.
• A version isolates user's work across multiple edit sessions, allowing the user to edit without locking features in the production version or immediately impacting other users.
• A geodatabase can have many versions. Below is the Version Manager dialog box accessed through ArcMap or ArcCatalog. It shows the DEFAULT version and three other versions: a quality assurance version (QA) and project versions, ProjectA and ProjectB.
  
  A geodatabase can have many versions
• In ArcCatalog or ArcMap, you can perform all of the same display, query, and editing functions on a version as you can on a nonversioned geodatabase.
• Users always access an ArcSDE geodatabase through a version. When you connect to a multiuser geodatabase in ArcCatalog or ArcMap, you specify the version to which you will connect. By default, you connect to the DEFAULT version.