EQL, an acronym for EXPRESS Query Language, is an SQL-like query language that is used to perform ad hoc queries on data in PART 21 files. PART 21 is the clear text encoding of data in the object-oriented EXPRESS modeling format and is the format for the STEP standards like AP203. Traditional uses for STEP files have been for transferring data between similar tools and populating a data model in one tool with the data from another tool. For example, moving a part design from one CAD system to another CAD system. If however, a software system has a different view of the information, a STEP file from one system contains significant amounts of data not applicable to other system. The receiving system needs the ability to query the STEP file for the objects important to its processing. Additionally, to integrate software systems using EXPRESS and PART 21 as a data transfer mechanism; an ad hoc query language is needed to account for the data in multiple schemas that a tool might expect to encounter. EQL is designed to accept data files in schemas that are not predefined to the tool and has the ability to perform all traditional data manipulation (DML) operations: select, update, insert and delete. EQL does not support data definition (DDL) like creating new object classes.