THEMES FROM 1972 
Robert F. Simmons 
Department of Computer Sciences 
University of Texas at Austin 
Austin, TX 78712 
Although 1972 was the year that Winograd 
published his now classic natural language Study 
of the blocks world, that fact had not yet 
penetrated to the ACL. At that time people with 
AI computational interests were strictly in a 
minority in the association and it was a radical 
move to appoint Roger Schank as program chairman 
for the year's meeting. That was also the year 
that we didn't have a presidential banquet, and my 
"speech" was a few informal remarks at the 
roadhouse restaurant somewhere in North Carolina 
reassuring a doubtful few members that 
computational understanding of natural language 
was certainly progressing and that applied natural 
language systems were distinctly feasible. 
My own perceptions of the state of 
computational linguistics during that period were 
given in "On Seeing the Elephant" in the Finite 
String, March-Aprll 1972. I saw it as a time of 
confusion, of competition among structuralists, 
transformationallsts, and the new breed of 
computernlks. "On Seeing the Elephant" was a 
restatement of the old Sufi parable that suggested 
that we each perceived only isolated parts of our 
science. 
That was the period during which Jonathan 
Slocum and I were concerned with using Augmented 
Transition Networks to generate coherent English 
from semantic networks. That llne of research was 
originated by the first President of the 
Association, Victor Yngve, who in 1960 had 
published descriptions of algorithms for using a 
phrase structure grammar to generate syntactically 
well-formed nonsense sentences \[Yngve 1960\]. 
Sheldon Klein and I about 1962-1964 were 
fascinated by the technique and generalized it to 
a method for controlling the sense of what was 
generated by respecting the semantic dependencies 
of words as they occurred in text. Yngve's work 
was truly seminal and it continued to inspire 
Sheldon for years as he developed method after 
method for generating detective stories and now 
operas. I, too, with various students continued 
to explore the generation side of language, most 
recently with Correlra \[1979\], using a form of 
story tree to construct stories and their 
summaries. No matter that Meehan found better 
methods and Bill Mann and his colleagues continue 
to improve on the techniques. The use of a phrase 
structure grammar to control the sequence in which 
sentences and words are p~oduced remains quite as 
fascinating as its use in translatln~ sentences to 
representations of meaning. 
It is possible to communicate the technique 
for controlled generation of text in Just a few 
paragraphs, so in dedication to Yngve, Klein, and 
i00 
the many others of the discipline who share our 
fascination with generation of meaningful 
language, the following description is presented. 
The last two lines of Keats" "Ode to a 
Grecian Urn" are: 
Beauty is truth, truth beauty, that is all 
Ye know on earth and all ye need to know. 
To form semantically controlled variations on this 
verse we can create substitution classes as below: 
\[SCLASS 
\[SCLASS 
\[SCLASS 
\[SCLASS 
\[SCLASS 
\[SCLASS 
\[SCLASS 
BEAUTY life knowledge wisdom love this\] 
TRUTH honor Joy rapture love all\] 
(THAT IS ALL)(that's all)(that's what) 
(it's all)(it's what)\] 
YE you we I some they\] 
KNOW sense have get see meet\] 
(ON EARTH) (for living)(til heaven) 
(til hell)(in llfe)\] 
(NEED TO) (have to)(ought to)(want to)\] 
and llne rules similar to phrase structure forms. 
(I think of the couplet as a three llne verse.) 
\[KLINEI beauty is truth -- truth beauty\] 
\[KLINE2 (that is all) ye know (on earth)\] 
\[KLINE3 (that is all) ye (need to) know\] 
Each KLINEi rewrites as a conjunction 
terms, e.g., 
KLINEI --> beauty + is + truth ... + beauty. 
of 
The line rules are composed of terms such as 
"beauty", "that is all", etc., that begin SCLASS 
predications, and of terminals such as "is" and "- 
-" that do not. Poem and verse can also be 
defined as rules: 
\[POEM title verse verse ... verse\] 
\[TITLE (Variation on Keats" Truth is Beauty)\] 
\[VERSE klinel kllne2 kllne3\] 
Actually it is more convenient to define these 
latter three elements as program to control choice 
of grammar, spacing, and number of verses. In 
either case, a POEM is a TITLE followed by VERSEs, 
an~ ~ VERSE is three lines each composed of 
terminals that occur in a KLINE or of selections 
from the matching substitution class. 
Only one other program element is required: a 
random selection function to pseudo-randomly 
choose an element from a substitution class and to 
record that element as chosen: 
((CHOOSE ( FIRST. REMDR) CHOICE) 
< (CHOSEN FIRS~ CHOICE)) 
((CHOOSE ( FYRST. REMDR) CHOICE) 
< (RANDOM* ( FIRST. REMI~R) CHOICE) 
(ASSERT (CHOSEN jHOICE))~ 
Note: CHOOSE is called with the 
content of an SCLASS rule in the list 
(FIRST.REMDR); if a choice for the 
term has previously been made in the 
verse, CHOICE is taken from the 
predicate, (CHOSEN FIRST CHOICE). If 
not, RANDOM* selects an element and 
records it as CHOSEN. When a verse is 
begun, any existing CHOSEN predicates 
are deleted. 
This is a procedural logic program with lists 
in dot notation and variables marked using the 
underscore. It is presented to give a sense of 
how the program appears in Dan Chester's LISP 
version of PROLOG. The rest of the program 
follows the poem, verse, and Keats-LINE rules 
given above. 
The program is called by (POGEN KEATS 4), 
KEATS selecting the grammar and 4 signifying the 
number of verses. A couple of recordings of its 
behavior appear below. 
*(POGEN KEATS 4) 
(VARIATIONS ON KEATS" TRUTH IS BEAUTY) 
(LOVE IS LOVE -- LOVE LOVE) 
(ITS ALL YE HAVE TIL HEAVEN) 
(ITS ALL YE NEED TO HAVE) 
(LOVE IS LOVE -- LOVE LOVE) 
(THATS ALL THEY KNOW ON EARTH) 
(THATS ALL THEY OUGHT TO KNOW) 
(WISDOM IS RAPTURE -- RAPTURE WISDOM) 
(ITS WHAT YOU MEET FOR LIVING) 
(ITS WHAT YOU WANT TO MEET) 
(LOVE IS ALL -- ALL LOVE) 
(THATS ALL WE SENSE TIL HELL) 
(THATS ALL WE HAVE TO SENSE) 
((POGEN KEATS 4)) 
*(POGEN KEATS 5) 
(VARIATIONS ON KEATS" TRUTH IS BEAUTY) 
(BEAUTY IS TRUTH -- TRUTH BEAUTY) 
(THATS WHAT YE SEE ON EARTH) 
(THATS WHAT YE WANT TO SEE) 
(KNOWLEDGE IS ALL -- ALL KNOWLEDGE) 
(ITS ALL THEY MEET TIL HELL) 
(ITS ALL THEY HAVE TO MEET) 
*** 
(LOVE IS RAPTURE -- RAPTURE LOVE) 
(ITS ALL SOME KNOW TIL HEAVEN) 
(ITS ALL SOME NEED TO KNOW) 
(LIFE IS RAPTURE -- RAPTURE LIFE) 
(THATS WHAT SOME GET FOR LIVING) 
(THATS WHAT SOME OUGHT TO GET) *** 
(LIFE IS LOVE -- LOVE LIFE) 
(ITS ALL I SENSE ON EARTH) 
(ITS ALL I WANT TO SENSE) *** 
((POGEN KEATS 5)) 
Perhaps these verses might best be 
characterized as those Keats wisely rejected. 
Nevertheless our robot-poet demonstrates the 
effectiveness of phrase structure organization and 
substitution classes for selecting and ordering 
actions. 
The ideas of Pogen led to related methods for 
creating paraphrases, answering questions, and 
translating between languages. The principle of 
phrase structure organization has permeated our NL 
efforts and found a particularly friendly 
environment in procedural logic where Chester and 
I \[1982\] show that the same grammar that 
translates English strings into semantic 
representations can serve to translate the 
representations into English strings. This 
result, confirming an earlier finding by Heldorn, 
greatly simplifies the linguistic programming 
requirements for NL translation and text 
questioning systems. 
Since 1972 the computational linguistics 
world has changed much. Today AI and Logic 
interests tend to overshadow linguistic approaches 
to language. But despite all the complexities in 
translating between NL constituents and 
computational representations, augmented phrase 
structure grammars provide a general and effective 
means to guide the flow of computation. 
REFERENCES 
Simmons, R.F., and Chester, D.L., "Relating 
Sentences and Semantic Networks with Procedural 
Logic," Communications of the ACM, September 
1982, (in press). 
Simmons, R.F., and Correira, A., "Rule Forms for 
Verse, Sentence, and Story Trees," in Findler, 
N.V., (ed.) Associative Networks, pp. 363-392, 
Academic Press, New York, 1979. 
Yngve, V., "A Model and a Hypothesis for Language 
Structure," Proceedings of the American 
\[hilosophical Society, pp. 444-466, 1960, 
Volume 104. 
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