Single EHR queries

A common use-case is to execute queries within a specific EHR.

This is achieved by supplying a ehr_id query parameter or setting a openEHR-EHR-id request header.

Population queries

Population queries are queries which are executed on several EHRs in the same request. These queries are not referring or using any ehr_id parameter to constrain the scope on a specific EHR.

Examples of use-cases can be:

• Ward lists,
• Explore correlations between patients in a pandemic situation,
• Research, e.g. epidemiology, population health.

Stored queries

Stored queries are queries which have their definition stored (registered) on the server. These are identified by their qualified name and version.

Using stored queries has several of advantages:

• separation of responsibilities (some users/developers write queries, others just call/execute them and consume the responses),
• no need to pass long query string over the network.

Queries can be stored or, once stored, their definition can be retrieved using the definition endpoint.

Ad-hoc queries

As opposed to stored queries, ad-hoc type queries does not have their definitions stored on the server, neither any associated identifier. These queries will be executed as-is, as part request body or query parameter, by the Execute ad-hoc AQL operation endpoint.