The Application Layer provides and integrates the process-related functionalities of the Work Line Connect^® standard with the application modules PP⁽¹⁾, MM⁽¹⁾, QM⁽¹⁾, PM⁽²⁾, CS⁽²⁾, PS⁽²⁾, I4⁽³⁾.

In service deliveries this layer will be overwritten module by module if necessary.

The most important objective of customizing for this layer is the dynamic mapping of the diverse data structures of the MES and SAP^© system, which can vary considerably from customer to customer, depending on their customizing of the systems involved and of the customer's functional requirements for the interconnected systems.

Any field in the MES system can be mapped to a corresponding field in the SAP^© system. The standard provides various types of mapping, like simple, static 1 to 1, field to field, condition-dependent (through boolean rules), calculated (eg for dimension conversion), table driven and programmed mappings.

In addition, the Application Layer provides user exits for docking customer-specific function blocks in the extension layer.