A Data Definition Language (DDL) is a standard for commands that define the different structures in a database. DDL files are provided to Market Participants from ERCOT in order to create a database that can be used to store the data received in ERCOT extracts into their own environments. The metadata provided in these files includes tables, columns, data type of each field, descriptions of the data that is to be loaded into each column and any table or character/precision constraints or alterations. As a general standard, DDLs are applied to define extracts that are provided in CSV format. However, some of the DDLs included here define the contents of report information in Excel as well.