Class Values

source code

                   object --+            
                            |            
 base.structure.StructureBase --+        
                                |        
                   object --+   |        
                            |   |        
           base.common.Parser --+        
                                |        
base.structure.ParseableStructure --+    
                                    |    
             base.structure.Structure --+
                                        |
                                       Values

Information on a column's values, in particular its domain.

This is quite like the values element in a VOTable. In particular, to accomodate VOTable usage, we require nullLiteral to be a valid literal for the parent's type.

Note that DaCHS does not validate for contraints from values on table import. This is mainly because before gavo values has run, values may not represent the new dataset in semiautomatic values.

With HTTP parameters, values validation does take place (but again, that's mostly not too helpful because there are query languages sitting in between most of the time).

Hence, the main utility of values is metadata declaration, both in the form renderer (where they become placeholders) and in datalink (where they are communicated as VOTable values).