Here are some (not necessarily) frequently asked questions and answers about (R)MRS.
- Q Are MRS predicates fixed arity? A Yes. This is required to make the models logically well-formed. Q Are MRSs feature structures? A No. Any hierarchies of predicates are also not type hierarchies. The suggested term is predicate hierarhcy, with the higher elements called "subsumers" and lower elements "subsumed".
Q What are the elements in hcons: qeq, lheq, and outscopes. A They are:
qeq - equality modulo quantifiers. A qeq constraint always relates a hole to a label. The intuition is that if a handle argument h is qeq to some label l, either that argument must be directly filled by l (i.e., h=l), or else one or more quantifiers ‘float in’ between h and l.
lheq - label-handle equality. The label and handle are constrained to be equated. Explicit equalities are used in various papers - the option of working with them rather than making the variables the same is useful theoretically and sometimes practically.
outscopes - directly or indirectly takes scope over. This is the relationship used by most work on underspecification. mentioned as an option in the MRS paper. Two possible versions: a) hole outscopes label - like qeq with no restriction to quantifiers b) label1 outscopes label2 - label1 must dominate label2 in all scope-resolved solutions. Not currently supported by the LKB scoping code in either case.
u := top. i := u. p := u. h := p. e := i & [ TENSE tense, MOOD mood, PERF luk, PROG luk, SF sforce ]. x := i & p & [ PERS person, NUM number, GEND gender, IND bool, DIV bool, PRONTYPE prontype ]. ;;; ;;; to check for `arity' in MTRs, sometimes we need an `anti-'variable type ;;; a := u.