Compositional Semantics - Computational Linguistics and Talking Robots - page 142

(iv) surface realization

1 2 3 4 5−6 7 8 9−10

quickly

11−12

That the little black dog found the_bone persuaded

13 14 15 16−17 18 19 20 21−22 23−24

. the pretty woman to_buy a nice new collar

All (1) subject / verb, (2) object \ verb, (3) modifier | modified, and (4)

conjunct conjunct relations are characterized explicitly in the (i) signature

and the (ii) semantic relations graph. The (iii) NAG provides the navigation
order used for the (iv) surface realization. Even though the signature is seman-
tic and has an initial node, it is not a semantic hierarchy . 27

−

Instead, the graph

is a constellation of binary semantic relations of structure. 28
The choice of which of two semantically related nodes must be the higher
one in the graph is not determined by the parts of speech, as witnessed by
the opaque constructions. Instead, it is determined by the semantic relation of
functor-argument or coordination between the two nodes, which in turn con-
strains the possible choices of the parts of speech. This holds at the elementary,
the phrasal, and the clausal level (3.5.6).
The SRG, the signature, and the NAG are alike in that they each have a
unique entry point at the highest level. Furthermore, to get to an argument,
the navigation must first traverse the functor; to get to a modifier, the naviga-
tion must first traverse the modified; and to get to a non-initial conjunct, the
navigation must first traverse the initial conjunct.
For example, in 7.6.6 the extrapropositional navigation entering the propo-
sition encounters the matrix verb first. From this entry point it proceeds to the
subject, which happens to be a sentential argument. From the lower verb, the
navigation continues through the first argument of the subject sentence, etc.
A navigation is driven by two complementary principles. The condition that
all nodes should be traversed during a navigation (9.1.4, 4) is called the down-
ward principle ; it ensures that a new branch is entered if one is available.
The condition that an intrapropositional navigation must end where it began
(9.1.5, 2) is called the upward principle ; it ensures that the navigation through
a branch returns to the beginning. This enables the downward principle to ap-
ply again until all nodes have been traversed. Finally, the upward principle
guides the navigation to the point of entry, i.e., the matrix verb.
Available branches at a given point in the navigation may be entered in differ-
ent orders. This is shown by the comparison between the active 9.1.3 and the

27 For example, there is no subclass or subtype relation between the V and the N in an N / V or any other
elementary signature. For the treatment of subclass relations in DBS see Sect. 6.5.