The current metadata document says that the schema property is optional, or, even if set, column, row, or cell properties are all optionals. What this means is that the names of the columns may not be available. If so, the current RDF/JSON conversion algorithms fail. A possibility is to define (in the metadata document) a default fall-back for column naming if there is nothing providing them. (Or requiring the presense of schema/column).

The discussion on a telco on the 1st of October put forward the approach of letting the conversion fail altogether; this is now reflected in the conversion documents.