@prefix iop: <https://w3id.org/iadopt/ont/> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix skos: <http://www.w3.org/2004/02/skos/core#> .
@prefix ex: <http://example.org/iadopt/challenge/> .
@prefix iopp: <https://w3id.org/iadopt/pattern/> .

ex:phvar
    a 
        iop:Variable ;
    rdfs:label 
        "pH measurement of a sample of apple juice" ;
    rdfs:comment 
        """pH of a sample of apple juice using a solid-state pH electrode""" ;
    iop:hasObjectOfInterest 
        <https://www.wikidata.org/wiki/Q618355> ;
    iop:hasProperty 
        <https://www.wikidata.org/wiki/Q40936> ;
    iop:hasConstraint 
        [ a iop:Constraint ;
             rdfs:label "defined by: hydronium ion activity" ;
             iop:constrains <https://www.wikidata.org/wiki/Q40936> ;
        ] .

<https://www.wikidata.org/wiki/Q618355>
    a 
        iop:Entity ;
    rdfs:label 
        "apple juice" .

<https://www.wikidata.org/wiki/Q40936>
    a 
        iop:Property ;
    rdfs:label 
        "pH" .