The Teachable Language Comprehender: 
A Simulation Program and Theory of Language
The Teachable Language Comprehender (TLC) is
a program designed to be capable of being taught 
to "comprehend" English text.  When text which the program
has not seen before is input to it, it comprehends 
that text by correctly relating each (explicit or implicit)
assertion of the new text to a large memory. 
 This memory is a "semantic network" representing factual
assertions about the world.  The program also 
creates copies of the parts of its memory which have
been found to relate to the new text, adapting and 
combining these copies to represent the meaning of the
new text.  By this means, the meaning of all text 
the program successfully comprehends is encoded into
the same format as that of the memory.  In this 
form it can be added into the memory.  Both factual
assertions for the memory and the capabilities for 
correctly relating text to the memory's prior content
are to be taught to the program as they are needed. 
 TLC presently contains a relatively small number of
examples of such assertions and capabilities, but 
within the system, notations for expressing either of these
are provided.  Thus the program now corresponds 
to a general process for comprehending language, and
it provides a methodology for adding the additional 
information this process requires to actually comprehend
text of any particular kind.  The memory structure 
and comprehension process of TLC allow new factual assertions
and capabilities for relating text to such 
stored assertions to generalize automatically.  That
is, once such an assertion or capability is put 
into the system, it becomes available to help comprehend
a great many other sentences in the future. 
 Thus the addition of a single factual assertion or
linguistic capability will often provide a large 
increment in TLC's effective knowledge of the world and
in its overall ability to comprehend text.  The 
program's strategy is presented as a general theory of language comprehension.
CACM August,1969
Quillian, M. R.
