Mystery Number Five - Computational Linguistics and Talking Robots - page 106

Due to the restriction on the variables , 6.5.4 is strictly equivalent to

6.5.3. From a linguistic point of view, 6.5.4 may be seen as the valency schema
(Herbst et al. 2004) or lexical frame of the transitive verb eat . The restriction
sets of the variables

α and β

may be established automatically by parsing a
corpus: all subjects of eat actually occurring in the corpus are written into
the restriction set of

α and β

α and all objects are written into the restriction set of β

(Sect. 8.5).
One of the many results of automatic schema derivation is the is-a hierarchy
(subsumptive containment hierarchy) familiar from knowledge representation
and object-oriented programming. As a subclass relation, the is-a hierarchy is
a prime example of the substitution approach because it is motivated more di-
rectly and more obviously than the constituent structure trees of Phrase Struc-
ture Grammar and Categorial Grammar.
The subclass relation between food as the hypernym and the set apple, pear,
salad, steak as the instantiation may be coded by extending the restriction
technique from variables to certain constants:

6.5.5 C ODING THE SUBCLASS RELATION FOR food
⎡
⎣

⎤
⎦

noun: food
fnc: β
prn: K

where food {apple, pear, salad, steak}
The hypernym concept food may serve as the literal meaning of the word food
in English, aliment in French, Nahrung in German, and so on.
The derivation of a semantic hierarchy, as illustrated in 6.5.3-6.5.5, is empir-
ically adequate if the resulting class containing the instantiations corresponds
to that of the surrounding humans. For example, if the artificial agent observes
humans to habitually (frequency) eat müsli, the restriction list of food must be
adjusted correspondingly. 22 Furthermore, the language surface, e.g., aliment ,
chosen by the artificial agent for the hypernym concept, e.g., food , must cor-
respond to that of the natural language in use.
Implicit in schema 6.5.5 is the following tree structure:

6.5.6 R EPRESENTING THE SEMANTIC HIERARCHY 6.5.5 AS A TREE

food

apple pear salad steak

22 This resembles the establishment of inductive inferences in logic, though based on individual agents.