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Processing Select Queries

 

Processing an OPM-QL select query Q can be divided into four steps:

  1. translating OPM query Q into one or more SQL queries;

  2. executing the SQL queries using the underlying relational DBMS;

  3. converting relational query results into an OPM representation;

  4. further processing the query results if necessary.

The query translation process is based on the mapping (metadata) information regarding the representation of classes in the relational database. We briefly discuss below three strategies for processing OPM queries.