7.1.2 SGML Grove Plan
The sgml-grove-plan element type form names additional modules that should be included in the grove plan for the SGML property set. The modadd attribute specifies the modules to be added. The following modules are included automatically:

•  baseabs

•  prlgabs0

•  instabs
For the transformation language, the prlgabs1 module is also included automatically.
This declaration is cumulative.