A grammar for writing dialogues, Robinson SRI 1980
large and complex grammar, DIAGRAM, that is used
in a computer system for interpreting English dialogue.
DIAGRAM analyzes all of the basic kinds of phrases
and sentencek and many quite complex ones as well.
It is not tied to a particular domain of application, and
it can be extended to analyze additional constructions,
using the formalism in which it is currently written.
For every expression it analyzes, DIAGRAM provides
an annotated description of the structural relations
holding among its constituents. The annotations provide
important information for other parts of the system
that interpret the expression in the context of a
DIAGRAM is an augmented phrase structure grammar.
Its rule procedures allow phrases to inherit attributes
from their constituents and to acquire attributes
from the larger phrases in which they themselves
are constituents. Consequently, when these attributes
are used to set context-sensitive constraints on the
acceptance of an analysis, the contextual constraints
can be imposed by conditions on dominance as well as
conditions on constituency. Rule procedures can also
assign scores to an analysis, rating some applications
of a rule as probable or as unlikely. Less likely analyses
can be ignored by the procedures that interpret
In assigning categories and writing the rule statements
and procedures for DIAGRAM, decisions were
guided by consideration of the functions that phrases
serve in communication as well as by considerations of
efficiency in relating syntactic analyses to propositional
content. The major decisions are explained and
illustrated with examples of the rules and the analyses
they provide. Some contrasts with transformational
grammars are pointed out and problems that motivate
a plan to use redundancy rules in the future are discussed.
(Redundancy rules are meta-rules that derive
new constituent-structure rules from a set of base
rules, thereby achieving generality of syntactic statement
without having to perform transformations on
syntactic analyses.) Other extensions of both grammar
and formalism are projected in the concluding section.
Appendices provide details and samples of the lexicon,
the rule statements, and the procedures, as well as
analyses for several sentences that differ in type and