Graph Theory - Computational Linguistics and Talking Robots - page 172

9.1.6 L INGUISTIC CONSTRAINTS ON WELLFORMED NAG S

1. An intrapropositional traversal must begin and end with the node which
actsastheverb. 4
2. The initial verbal node must be entered either by arc 0 or by a correspond-
ing arc from a preceding proposition (7.4.4).
3. The only lines permitted in a NAG are “ / ” (subject-verb), “ \ ” (object-

” (conjunct-conjunct).
4. The only nodes permitted in a NAG based on a signature are N (noun), V
(verb), and A (adjective).
Condition 1 excludes the two NAGs on the right in 9.1.5. Because they do not
begin and end with the verb, they cannot be coordinated with other proposi-
tions (cf. extrapropositional coordination 7.4.4 and 9.2.1).
The remaining two NAGs on the left in 9.1.5, in contrast, are linguistically
wellformed. They are used for realizing the free word order of Russian (7.4.5)
as well as the alternation between active and passive 5 in English:

verb), “ | ” (modifier-modified), and “ −

9.1.7 D ERIVING E NGLISH PASSIVE FROM CONTENT 9.1.3

(i) semantic relations graph (SRG) (iii) numbered arcs graph (NAG)

find

0

find

2

3 4

dog bone 1

dog bone

(iii) signature

V

(iv) surface realization

1 2 3 4

.

A_bone was_found by_the_dog

NN

The semantic relations and the signature of the passive are the same as in the
active 9.1.3, while the NAG and the surface realization are different: the active
uses the first NAG in 9.1.5, while the passive uses the second.

9.2 Extrapropositional Coordination

Extrapropositional coordination is bidirectional insofar as content may be tra-
versed in the temporal and the anti-temporal direction (cf. NLC'06, Sect. 9.6).
As an example, consider the following signature representing the content John
leave house. John cross street. :