Separation principle: Approach 1 (external separation)

The data custodian applies the separation principle before providing data to the integrating authority

One broad approach for data custodians preparing their datasets for integration under the Commonwealth arrangements is to apply the separation principle themselves before providing data to the integrating authority. (SA NT DataLink commissioned an educational animation to describe the two-part separation principle.)

This approach involves the following key steps:

Step 1: the data custodians separate the identifying information from content data;

Step 2: the data custodians send encrypted identifying information to the Data Linkage Unit at the nominated integrating authority for the creation of a linkage key file (the integrating authority may choose to outsource the creation of linkage keys to a third party Data Linkage Unit (see Outsourcing and working in partnership)

Step 3: the data custodians send encrypted content data (without the identifying information) to the Data Merging Unit at the nominated integrating authority to merge the datasets.

Example of applying the separation principle using a linkage key approach

These key steps are illustrated in the diagram below using an example of data flows involving State Cancer Registry data and Medical Benefits data. The key steps shown in this example are:

  • Linkage – in this example, both datasets contain linking, (or identifying) information (name, date of birth, sex, postcode) which is extracted by the data custodians and sent to the integrating authority (linkage unit). This information is used to create a Project ID that is linked to the Local ID on both custodian files.
  • Merging – the data custodian subsequently provides the required analysis (or content) data (cancer diagnosis; date of service) and the Local ID to the integrating authority. The two datasets are merged for each Project ID using the Local ID.
  • Access – only the Project ID and the content data are included on the integrated dataset. The integrating authority confidentialises this integrated dataset as necessary and provides secure access to data users/researchers. 


The Australian Institute of Health and Welfare (AIHW) offers various separation options to data custodians during project initiation. Details can be found in the AIHW's application for integrating authority accreditation summary.

For more information about applying the separation principle see: