Not support to rr:joinCondition RML property

[dachafra]

Our mappings contain rr:joinCondition properties in some POMs but it seems that the engine does not support it as it outputs: ERROR: Relevant source detected but cannot be read due to mappings issues. For example, are you using rr:parentTriplesMap instead of rml:reference.

First: the substitution should be usually done by rr:template as the object of the triple generating by a POM with rr:joinCondition is the subject of other triplesMap
Second: the output of using rr:template or rr:joinCondition can be totally different, as with the use of rr:template we are not ensuring that the value already exists in the rml:logicalSource of the rr:parentTriplesMap, hence, this option could generate incorrect results.

Logs of an example of a join between two tables of BSBM:
log_spark.txt
log_presto.txt