Boolean expressions

A boolean expression combines properties of attributes and context:

  boolexp  ->  <And> boolexp* </And> |
               <Or> boolexp* </Or> |
               <OneOf> boolexp* </OneOf> |
               <Not> boolexp* </Not> |
               <Imply> boolexp boolexp </Imply> |
               <Equiv> boolexp* </Equiv> |
               attributedescr |
               <Context> contextexp </Context>

Boolean expressions are used as

constraints,
guards in conditional constraints,
guards in conditional content expressions (later...),
guards in defaults (later...),
points-to expressions (later...).