diff --git a/data-discovery/src/main/java/webapi/formatfilter/ObscoreExt.java b/data-discovery/src/main/java/webapi/formatfilter/ObscoreExt.java
index f9be0fb4264e85401673060de5c99d1d0287aa3e..fea98452390ab391c6d3d684292f16871281da3c 100644
--- a/data-discovery/src/main/java/webapi/formatfilter/ObscoreExt.java
+++ b/data-discovery/src/main/java/webapi/formatfilter/ObscoreExt.java
@@ -1,17 +1,27 @@
 
 
 import uk.ac.starlink.table.*;// ColumnInfo needed
+import uk.ac.starlink.votable.*;
 
 class ObscoreExt
 {
+   static private ColumnInfo genPubDidColInfo()
+   {
+      ColumnInfo colInfo = new ColumnInfo( "obs_publisher_did", String.class,  "Publisher Did" );
+      colInfo.setAuxDatum(new DescribedValue(VOStarTable.ID_INFO, "primaryID"));
+      return colInfo;
+   }
+
+
    public static final ColumnInfo[] OBSCORE_COLINFO =
    {
+
       new ColumnInfo( "dataproduct_type",  String.class,  "Dataproduct Type (image|cube)" ),
       new ColumnInfo( "calib_level",       Integer.class, "Calibration level" ),
       new ColumnInfo( "obs_collection",    String.class,  "Collection" ),
       new ColumnInfo( "obs_title",         String.class,  "Title" ),
       new ColumnInfo( "obs_id",            String.class,  "Observation Id" ),
-      new ColumnInfo( "obs_publisher_did", String.class,  "Publisher Did" ),
+      genPubDidColInfo(),
       new ColumnInfo( "bib_reference",     String.class,  "Bibbliographic refererence" ),
       new ColumnInfo( "data_rights",       String.class,  "Data rights" ),