// game instance example

GameInstance =
<values> 
<vars> Ident
<inst> FileName




language for defining object properties:

per field
  if List: length: NumberConstraint(Integer)
	   randomly choose length
           element: List(ElementConstraint)
	   (randonly choose element satisfying ElementConstraint) 
  if abstract: (randomly choose alternative)
  if concrete: one choice only
     if Integer: NumberConstraint(Integer)
     if Float: NumberConstraint(Float)
     if Ident: regexp
     if String: regexp


NumberConstraint(T) :
  Single(T) | Range(T) | Enumeration(T) | Ref.
Single(T) = <v> T.
Range = "range" <low> T <high> T.
Enumeration(T) = "enum" <l> List(T).
Ref = <v> QualIdent.
QualIdent = <first> Ident <rest> List(DField).
DField = "." Field.

ElementConstraint : Distinct | In | Subset.
In = "in" Ref.
Subset = "subset" Ref.
Distinct = "distinct".

apply to CSP:

predicate: <rns> List(Integer)

CSP:
<vs> List(Variable)
<cs> List(Constraint).

Constraint = <w> Weight <rn> Integer <vars> List(Variable).
property: rn in predicate.rns
property: vars subset start.cs 




refer to earlier fields in predicate or current cd.