| 摘要 |
A middle-tier Web server with a queryable cache that contains items from one or more data sources. Items are included in the cache on the basis of the probability of future hits on the items. When the data source determines that an item that has been included in the cache has changed, it sends an update message to the server, which updates the item if it is still included in the cache. As disclosed, the data source is a database system and triggers in the database system are used to generate update messages. The data access layer determines whether a data item required by an application program is in the cache. If it is, the data access layer obtains the data item from the cache; otherwise, it obtains it from the data source. The Web application programs use global data set identifiers to identify data sets, while the cached data sets are identified by local data set identifiers. The cache receives a query context of global data set identifiers, determines whether the data sets of the query context are cached, and if they are, provides the local data set identifiers for the query context to the access layer, which then uses the local data set identifiers to query the cache. |
