There are several approaches to writing programs that query PGDBs:
aic-export/ecocyc directory, such
as in directory aic-export/ecocyc/metacyc/released/data/. However, you can also generate flat file versions of any PGDB by invoking the Pathway/Genome Navigator command Special / Misc / File Export / Dump KB to flat files.
The format of Pathway Tools flat files is described in detail in this Web page. The meaning of the fields in the flat files is described in Appendix I of the first volume of the Pathway Tools User's Guide.