The links between different data objects are essential for the provenance collection and the contextual knowledge of different aspects of the workflow. CWL provides these links between different entities in the description document. For example, it depicts that output from sub-workflow 1 is used as input for sub-workflow 2. These links can be more meaningful by adding contextual metadata. Another way to link the references to metadata is to use DOIs of the individual steps, tools, or input files.