| 摘要 |
A database querying system to facilitate the retrieval of desired data from a database including information categories, object data items, a processor assembly responsive to a user query, a relationship category defined by relationships between the object data items of the information categories, the user query including a relationship identifier corresponding to the relationship category. Interpretation of relational-database query and data manipulation languages against non-relational schemas, by regarding the schemas as representing virtual relational databases with every class replaced by a virtual table comprised of all the attributes reachable from the class by a chain of relations. The interpretation allows concise and simple querying of non-relational and relational databases in languages originally intended only for relational databases. The system further provides wrapping of a relational database into a semantic conceptual schema to allow formulation of queries in SQL against the wrapping schema, reducing the size of SQL queries.
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