---+ Using BioCASE operators

*Description:* 

For DiGIR it means:

   * creating a new unary logical operator called*not*.

   * dropping the logical operators*andNot* and*orNot*.

   * creating two new comparative operators called*isNull* and*isNotNull* to query for "NULL" values

*Impact:* DigirPortalPresentation, DigirProvider (filter builder and local filters in the configurator) 

*Comments:*