Syntax of Segmented Discourse Representation Structures (SDRSs)

The Prolog syntax of Segmented DRSs is defined below in BNF:

<sdrs> ::= sdrs(<refs>,<labels>,<constraints>) 

An SDRS is a tuple consisting of a set of DRS-referents, a set of labelled (S)DRSs, and a set of constraints:

<refs> ::= [<referent>{,<referent>}]

<labels> ::= [lab(<referent>,<sem>){,lab(<referent>,<sem>)}]

<sem> ::= <drs> |
          <sdrs>

<constraints> ::= [] |
                  [<rel(<referent>,<referent>,<relation>)
                   {,<rel(<referent>,<referent>,<relation>)}]