AQL descendant paths (feature discussion)

In the AQL v1.0 we have this example, that includes "//*" in a path, which is not currently supported by AQL:

[cols="1,4a",options="header",separator=¦]
|===

¦*Clinical Scenario 1*      ¦Require all blood pressure values with position recorded

¦*AQL Fragment*             ¦
----
SELECT o
FROM
   EHR e CONTAINS
      COMPOSITION CONTAINS
         OBSERVATION o [openEHR-EHR-OBSERVATION.blood_pressure.v1]
WHERE 
   exists {"o//*/state[at0007]/items[at0008]"}
----
|===

On https://discourse.openehr.org/t/aql-new-feature-suggestion-descendant-paths/320/4 most agree on this is not currently supported so I suggested to remove the example from the spec and keep it on the WIKI for further discussion of the "descendant path".

This is the WIKI page to continue analyzing if descendant paths are useful, detect use cases (if any), etc.