There are the following built-in types in the TIGER language:
String for feature values not listable such as the values of
the features word or lemma
UserDefConstant for user-defined ('listable') feature values
Constant comprises both String and
UserDefConstant
NT for feature constraints of nonterminal nodes
T for feature constraints of terminal nodes
FREC stands for all feature records (feature constraints),
i.e. NT and T
Node stands for node descriptions
Graph means all graphs
Top means anything (in the world of syntax graphs)
The hierarchy of built-in types is visualized in the following figure. Defining a type hierarchy is introduced in the following subsection.
Figure: Built-in types
The built-in types Top, Node and Graph are only required on the conceptual level. In the current implementation, they cannot be referred to in the description language.