Quantifying conversion efficacy

|e_p| - |v_p| / |v_p| vs. |e_l| - |v_l|

enhance, verbatim, param, layer

DRAFT:

PREFIX void:       <http://rdfs.org/ns/void#>
PREFIX conversion: <http://purl.org/twc/vocab/conversion/>

SELECT *
WHERE {
  GRAPH <http://logd.tw.rpi.edu/vocab/Dataset> {
    ?versioned 
       a conversion:VersionedDataset;
       void:subset ?layerD
    .
    ?layerD 
       a conversion:LayerDataset; 
       conversion:conversion_identifier ?layer
    .
    {OPTIONAL {?layerD conversion:num_triples ?triples}}
    UNION
    {OPTIONAL {?layerD void:subset [ a conversion:Dataset; 
                                     conversion:num_triples ?triples ]}}
  }
}