whole_func_string: function ConstraintEqualTo (value) {
      this.describe = function (varstr) { return varstr + ' = ' + value.toNT() }
      this.test = function (term) {
        return value.sameTerm(term)
      }
      return this
    }
func_code_string: function ConstraintEqualTo (value) {
      this.describe = function (varstr) { return varstr + ' = ' + value.toNT() }
      this.test = function (term) {
        return value.sameTerm(term)
      }
      return this
    }
func_documentation_string: See ../rdf/sparql.js This should only work on literals but doesn't.