Relationship between template and instance

All parties authorized to act as producers in a given environment can create and evolve e-service templates. To create a new template, go to Producing > Your templates and click on Create new.
The creation of a template is very similar to that of an e-service: in fact, a template contains the same fields as an e-service. The only difference is that there is an extra field for the template description with potential explanatory notes, intended to support parties interested in deriving their own instance.

Similarly, all parties authorized to act as producers in a given environment can create instances from templates. They can do this via Producing > Template catalog, selecting the desired template and clicking on Use template to generate their own instance.

As described in the dedicated section, the definition of attributes is at the discretion of the template creator. The party deriving its instance from the template cannot modify them independently. If they believe there are inconsistencies, they must contact the template creator, who may correct them.

As with any other e-service, the attributes of the instance are the ones that will be required from potential consumers in order to submit a service request.

The states of a template and those of e-services instantiated from it are completely independent from one another. When a producer instantiates their e-service from a template, it does not inherit the template’s state updates.

For example, if a template is suspended while the instantiated e-service is active, the e-service remains active. Likewise, a producer can archive their instance of an e-service without affecting the template.

An e-service template can be updated over time. These updates are categorized as either minor or critical.

Minor updates are propagated immediately to all instances. For example, if an error is identified and corrected in the template description, that correction will automatically appear in all e-service instances derived from that template.

Critical updates involve structural changes to the API interface, for which the template creator generates a new version of the template. In such cases, instances cannot be updated automatically. Each party that instantiated an e-service from the template must update it manually after making the necessary technical adjustments.

Due to its critical nature, this update results in a new version of the e-service instance. Consequently, all consumers must update their service request to the latest version of the e-service after completing tests and technical updates, just like with any other e-service.

If a party has published an e-service instance and needs to update it (e.g., to change the server URL or audience), a new version of the e-service instance must be created—just as with any e-service.

In this scenario, the version of the e-service instance may diverge from that of the template (e.g., the template may be at version 2 while the instance is at version 3).