You can define a key in the resource definition. When you define a key, the Data Integration Service indexes the column in the output data. A web service client can request specific output rows by key.
When you create a resource from a data object, the Developer tool uses a primary key from the data object as the resource key by default. If the primary key contains multiple columns, the Developer tool delimits the column data with "+" to create the primary keys.
You can configure the Developer tool to use a different output column as a primary key than the primary key of the source.
When you manually create a resource, the resource key must be an element with a simple type.