| 摘要 |
A database management protocol exchanges update tokens between a client and a server on which the database resides. When a client requests data to be read from a database, an update manager either reads an update token stored therein or generates one dynamically. The update token represents a current state of the data object being read. Sometime thereafter, if the client requests new data to be stored in the object, the client may furnish the update token back to the update manager. The update manager compares the client's update token to a local update token representing a current state of the database and, if they match, determines that the state has not changed. If they do not match, an error results.
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