Carl Eddie Hewitt () is an American computer scientist who designed the Planner programming language for automated planningCarl Hewitt
''PLANNER: A Language for Proving Theorems in Robots''
IJCAI. 1969. and the

actor model The actor model in computer science is a mathematical model of concurrent computation that treats ''actor'' as the universal primitive of concurrent computation. In response to a message it receives, an actor can: make local decisions, create mor ...

of concurrent computation, which have been influential in the development of

logic Logic is the study of correct reasoning. It includes both formal and informal logic. Formal logic is the science of deductively valid inferences or of logical truths. It is a formal science investigating how conclusions follow from prem ...

functional Functional may refer to: * Movements in architecture: ** Functionalism (architecture) ** Form follows function * Functional group, combination of atoms within molecules * Medical conditions without currently visible organic basis: ** Functional sy ...

and

object-oriented programming Object-oriented programming (OOP) is a programming paradigm based on the concept of "objects", which can contain data and code. The data is in the form of fields (often known as attributes or ''properties''), and the code is in the form of ...

. Planner was the first

programming language A programming language is a system of notation for writing computer programs. Most programming languages are text-based formal languages, but they may also be graphical. They are a kind of computer language. The description of a programming ...

based on procedural plans invoked using pattern-directed invocation from assertions and goals. The actor model influenced the development of the

Scheme A scheme is a systematic plan for the implementation of a certain idea. Scheme or schemer may refer to: Arts and entertainment * ''The Scheme'' (TV series), a BBC Scotland documentary series * The Scheme (band), an English pop band * ''The Schem ...

programming language, the π-calculus, and served as an inspiration for several other programming languages.

Education and career

Hewitt obtained his

PhD PHD or PhD may refer to: * Doctor of Philosophy (PhD), an academic qualification Entertainment * '' PhD: Phantasy Degree'', a Korean comic series * '' Piled Higher and Deeper'', a web comic * Ph.D. (band), a 1980s British group ** Ph.D. (Ph.D. al ...

in mathematics at MIT in 1971, under the supervision of Seymour Papert,

Marvin Minsky Marvin Lee Minsky (August 9, 1927 – January 24, 2016) was an American cognitive and computer scientist concerned largely with research of artificial intelligence (AI), co-founder of the Massachusetts Institute of Technology's AI laboratory ...

, and Mike Paterson. He began his employment at MIT that year, and retired from the faculty of the MIT Department of Electrical Engineering and Computer Science during the 1999–2000 school year. He became emeritus in the department in 2000. Among the doctoral students that Hewitt supervised during his time at MIT are Gul Agha, Henry Baker, William Clinger,

Irene Greif Irene Greif is an American computer scientist and a founder of the field of computer-supported cooperative work (CSCW). She was the first woman to earn a Ph.D. in computer science from the Massachusetts Institute of Technology. Biography Greif's ...

, and

Akinori Yonezawa is a Japanese computer scientist specializing in object-oriented programming, distributed computing and information security. Being a graduate of the University of Tokyo, Yonezawa has a Ph.D in computer science from MIT in the Actor group at th ...

. From September 1989 to August 1990, Hewitt was the IBM Chair Visiting Professor in the Department of Computer Science at

Keio University , mottoeng = The pen is mightier than the sword , type = Private research coeducational higher education institution , established = 1858 , founder = Yukichi Fukuzawa , endowment ...

in Japan. He has also been a Visiting Professor at

Stanford University Stanford University, officially Leland Stanford Junior University, is a private research university in Stanford, California. The campus occupies , among the largest in the United States, and enrolls over 17,000 students. Stanford is conside ...

Research

Hewitt is best known for his work on the

of computation. For the last decade, his work has been in "inconsistency robustness", which aims to provide practical rigorous foundations for systems dealing with pervasively inconsistent information. This work grew out of his doctoral dissertation focused on the procedural (as opposed to logical) embedding of knowledge, which was embodied in the Planner programming language. His publications also include contributions in the areas of open information systems, organizational and

multi-agent system A multi-agent system (MAS or "self-organized system") is a computerized system composed of multiple interacting intelligent agents.Hu, J.; Bhowmick, P.; Jang, I.; Arvin, F.; Lanzon, A.,A Decentralized Cluster Formation Containment Framework fo ...

logic programming Logic programming is a programming paradigm which is largely based on formal logic. Any program written in a logic programming language is a set of sentences in logical form, expressing facts and rules about some problem domain. Major logic pro ...

concurrent programming Concurrent means happening at the same time. Concurrency, concurrent, or concurrence may refer to: Law * Concurrence, in jurisprudence, the need to prove both ''actus reus'' and ''mens rea'' * Concurring opinion (also called a "concurrence"), ...

paraconsistent logic A paraconsistent logic is an attempt at a logical system to deal with contradictions in a discriminating way. Alternatively, paraconsistent logic is the subfield of logic that is concerned with studying and developing "inconsistency-tolerant" syst ...

and

cloud computing Cloud computing is the on-demand availability of computer system resources, especially data storage ( cloud storage) and computing power, without direct active management by the user. Large clouds often have functions distributed over mu ...

Planner

The Planner language was developed during the late 1960s as part of Hewitt's doctoral research in MIT's Artificial Intelligence Laboratory. Hewitt's work on Planner introduced the notion of the "procedural embedding of knowledge", which was an alternative to the logical approach to knowledge encoding for

artificial intelligence Artificial intelligence (AI) is intelligence—perceiving, synthesizing, and inferring information—demonstrated by machines, as opposed to intelligence displayed by animals and humans. Example tasks in which this is done include speech ...

pioneered by John McCarthy. Planner has been described as "extremely ambitious". A subset of Planner called Micro-Planner was implemented at MIT by

Gerry Sussman Gerald Jay Sussman (born February 8, 1947) is the Panasonic Professor of Electrical engineering, Electrical Engineering at the Massachusetts Institute of Technology (MIT). He received his Bachelor of Science, S.B. and Doctor of Philosophy, Ph.D. ...

, Drew McDermott,

Eugene Charniak Eugene Charniak is a professor of computer Science and cognitive Science at Brown University. He holds an A.B. in Physics from the University of Chicago and a Ph.D. from M.I.T. in Computer Science. His research has always been in the area of l ...

and

Terry Winograd Terry Allen Winograd (born February 24, 1946) is an American professor of computer science at Stanford University, and co-director of the Stanford Human–Computer Interaction Group. He is known within the philosophy of mind and artificial intel ...

Gerry Sussman and Terry Winograd.
Micro-planner Reference Manual
' AI Memo No, 203, MIT Project MAC, July 1970. and was used in Winograd's SHRDLU program,Terry Winograd.
Procedures as a Representation for Data in a Computer Program for Understanding Natural Language
' MIT AI TR-235. January 1971. Charniak's natural language story understanding work,Marvin Minsky and Seymour Papert. "Progress Report on Artificial Intelligence" MIT AI Memo 252. 1971. and L. Thorne McCarty's work on legal reasoning. Planner was almost completely implemented in PoplerJulian Davies. Popler 1.6 Reference Manual University of Edinburgh, TPU Report No. 1, May 1973. by Julian Davies at Edinburgh. Planner also influenced the later development of other AI research languages such as Muddle and Conniver, as well as the

Smalltalk Smalltalk is an object-oriented, dynamically typed reflective programming language. It was designed and created in part for educational use, specifically for constructionist learning, at the Learning Research Group (LRG) of Xerox PARC by Alan ...

object-oriented programming language. Hewitt's own work on Planner continued with Muddle (later called MDL), which was developed in the early 1970s by Sussman, Hewitt, Chris Reeve, and David Cressey as a stepping-stone towards a full implementation of Planner. Muddle was implemented as an extended version of

Lisp A lisp is a speech impairment in which a person misarticulates sibilants (, , , , , , , ). These misarticulations often result in unclear speech. Types * A frontal lisp occurs when the tongue is placed anterior to the target. Interdental lispin ...

, and introduced several features that were later adopted by Conniver, Lisp Machine Lisp, and Common Lisp. However, in late 1972 Hewitt abruptly halted his development of the Planner design in his thesis, when he and his graduate students invented the

of computation.

Actor model

Hewitt's work on the

of computation has spanned over 30 years, beginning with the introduction of the model in a 1973 paper authored by Hewitt, Peter Bishop, and Richard Steiger, and including new results on actor model semantics published as recently as 2006.Carl Hewit
''What is Commitment? Physical, Organizational, and Social''
COIN@AAMAS. April 27, 2006. Much of this work was carried out in collaboration with students in Hewitt's Message Passing Semantics Group at MIT's Artificial Intelligence Lab. Sussman and Steele developed the Scheme programming language in an effort to gain a better understanding of the actor model. However, their Scheme interpreter was not capable of fully implementing the actor model because actor customers cannot be implemented as lambda calculus continuations and actors can change their local state in a way that is impossible in the lambda calculus A number of programming languages were developed to specifically implement the actor model, such as ACT-1,

SALSA Salsa most often refers to: * Salsa (Mexican cuisine), a variety of sauces used as condiments * Salsa music, a popular style of Latin American music * Salsa (dance), a Latin dance associated with Salsa music Salsa or SALSA may also refer to: A ...

, Caltrop, E and ActorScript. The actor model also influenced the development of the π-calculus.Robin Milner Elements of interaction: Turing award lecture CACM. January 1993. (See actor model and process calculi history.)

Selected works

* Carl Hewitt (1969)
''PLANNER: A Language for Proving Theorems in Robots''
IJCAI'69. * Carl Hewitt, Peter Bishop and Richard Steiger (1973). ''A Universal Modular Actor Formalism for Artificial Intelligence'' IJCAI'73. * Carl Hewitt and Henry Baker (1977a). ''Laws for Communicating Parallel Processes'' IFIP'77. * Carl Hewitt and Henry Baker (1977b)
''Actors and Continuous Functionals''
Proceeding of IFIP Working Conference on Formal Description of Programming Concepts. August 1–5, 1977. * William Kornfeld and Carl Hewitt (1981)
''The Scientific Community Metaphor''
IEEE Transactions on Systems, Man, and Cybernetics. January 1981. * Henry Lieberman and Carl E. Hewitt (1983)

Communications of the ACM, 26(6). * Carl Hewitt (1985). ''The Challenge of Open Systems'' Byte Magazine. April 1985. (Reprinted in ''The foundation of artificial intelligence—a sourcebook'' Cambridge University Press. 1990

References

External links

* *
Hewitt's official blog
{{DEFAULTSORT:Hewitt, Carl Year of birth missing (living people) Living people American computer programmers American computer scientists 20th-century American mathematicians 21st-century American mathematicians Formal methods people MIT School of Engineering faculty Keio University faculty American technology writers Engineers from Massachusetts