Elephant 2000: A Programming Language Based on Speech Acts
John McCarthy, Stanford University
I meant what I said, and I said what I meant.
An elephant's faithful, one hundred percent!
An elephant never forgets!
Elephant 2000 is a proposed programming language good for writing
and verifying programs that interact with people (e.g. transaction
processing) or interact with programs belonging to other
organizations (e.g. electronic data interchange)
- Communication inputs and outputs are in an I-O language whose
sentences are meaningful speech acts identified in the language as
questions, answers, offers, acceptances, declinations, requests,
permissions and promises.
- The correctness of programs is partly
defined in terms of proper performance of the speech acts. Answers
should be truthful and responsive, and promises should be kept.
Sentences of logic expressing these forms of correctness can be
generated automatically from the form of the program.
- Elephant source programs may not need data structures, because
they can refer directly to the past. Thus a program can say that an
airline passenger has a reservation if he has made one and hasn't
- Elephant programs themselves can be
represented as sentences of logic. Their extensional properties
follow from this representation without an intervening theory of
programming or anything like Hoare axioms.
programs that interact non-trivially with the outside world can have
both input-output specifications, relating the programs inputs
and outputs, and accomplishment specifications concerning what
the program accomplishes in the world. These concepts are
respectively generalizations of the philosophers'
illocutionary and perlocutionary speech acts.
- Programs that engage in commercial transactions assume
obligations on behalf of their owners in exchange for obligations
assumed by other entities. It may be part of the specifications of
an Elephant 2000 programs that these obligations are exchanged as
intended, and this too can be expressed by a logical sentence.
- Human speech acts involve intelligence. Elephant 2000 is on the
borderline of AI, but the article emphasizes the Elephant usages
that do not require AI.
Fri Nov 6 21:37:30 PST 1998