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.
