12. Prodata as a Tool for Standard Query Language

This sesion describes the Prodata LPA Prolog interface which is a tight coupling between LPA-PROLOG for Windows and all DataBase Management Systems (DBMSs) which support a sufficient level of Open DataBase Connectivity (ODBC) compliance to be used with Microsoft ODBC 2.

Prodata allows database tables to be accessed from Prolog as though they existed within Prolog's environment as unit ground clauses (facts). This facilitates the use of Prolog rules over the contents of the database, with no need to download any part of the database, as all database accesses are done 'on-the-fly'. Backtracking, cut, call, not and all other standard Prolog mechanisms work identically over the table accesses and the internal database, thus achieving the highest level of transparency possible.

This software architecture allows a completely different style of database programming that leaves fourth generation languages way behind. All the benefits inherent in Prolog development can now be transferred to the database field without any disadvantages.

Prodata offers the following functionality:

• Concurrent access and update, with program control;
• Full data access transparency;
• All database functions can be carried out from within Prolog, such as creating tables, adding/deleting records, allocating access rights; in fact whatever may be achieved via normal Structured Query Language (SQL), just as long as the ODBC driver supports it;
• Optional automatic display of error messages produced by the database system;
• Automatic data conversions;
• Full access to the data dictionary, for those DBMSs which have one;
• Completely transparent cursor manipulation: there is never any need for your program to manipulate the table cursors.
• It is possible to see the SQL generated for a Prolog access to the DBMS by the use of specially provided predicates.
• Date types are handled uniformally across all Relational DataBase Management Systems (RDBMS).
• All DBMSs with ODBC compliant drivers are supported.
• Simultaneous connection to multiple DBMS is now possible, allowing table joins across database systems.

All facilities are available for all the supported DBMSs unless otherwise stated; the supported DBMSs include: Access, SQL Server, Oracle, DB2, dBase, Excel.