AQL Proposed Local Variables (discussion)

This was taken out from the AQL v1.0.0 specification, since it is not related with the spec and it’s a proposed feature that needs analysis and consensus.

1.6. Further discussions

The existing AQL grammar and syntax could be further enhanced in the following areas:

Reduce the length of the query statement. The use of archetype path in AQL query makes the query lengthy and hard to read. Local variables with meaningful names that are assigned with path can be used to reduce the length of the query as well as improve readability of the query. One example is shown below:

let $systolic_bp="data[at0001]/events[at0006]/data[at0003]/items[at0004]/value/magnitude"
let $diastolic_bp="data[at0001]/events[at0006]/data[at0003]/items[at0005]/value/magnitude"

SELECT
    obs/$systolic_bp, obs/$diastolic_bp
FROM
    EHR [ehr_id/value=$ehrUid] CONTAINS COMPOSITION [openEHR-EHR-COMPOSITION.encounter.v1]
        CONTAINS OBSERVATION obs [openEHR-EHR-OBSERVATION.blood_pressure.v1]
WHERE
    obs/$systolic_bp>= 140 OR obs/$diastolic_bp>=90

Tasks:

Discuss with SEC members pros? cons? value? workarounds?
Decide upon it’s support for next versions of AQL or discard the idea and close the discussion.