A schema defines the data structure and record types for sources, lookups, temporary targets, and targets in a map. In some cases, a schema provides connector-specific metadata for data handling. Schema are used to map source fields to target fields. They are also used to validate data against an expected schema format. Finally, schema are used by the engine to parse data that is read on the source side and format data written on the target side.

A schema consists of:

The Schema Editor provides a visual user interface for designing the format and structure of the map input (source) and output (target) data. The resulting metadata is stored as schema files with the .schema extension. Using the Schema Editor, you can create or modify the schema used in a map to provide a structure for the sources and targets files. Schemas are particularly important when connections to data do not contain metadata that describes the data. All existing database tables contain metadata that describe the data format. Some data, however, do not have data structure descriptions. In these cases, a schema must be provided.