Micro-Planner (programming language)

Planner (often seen in publications as "PLANNER" although it is not an acronym) is a programming language designed by Carl Hewitt at MIT, and first published in 1969. First, subsets such as Micro-Planner and Pico-Planner were implemented, and then essentially the whole language was implemented as ''Popler'' by Julian Davies at the University of Edinburgh in the POP-2 programming language.Carl Hewitt Middle History of Logic Programming: Resolution, Planner, Prolog and the Japanese Fifth Generation Project ArXiv 2009. Derivations such as QA4, Conniver, QLISP and Ether (see scientific community metaphor) were important tools in artificial intelligence research in the 1970s, which influenced commercial developments such as Knowledge Engineering Environment (KEE) and Automated Reasoning Tool (ART).

Procedural approach versus logical approach

The two major paradigms for constructing semantic software systems were procedural and logical. The procedural paradigm was epitomized by
Lisp cCarthy ''et al.'' 1962which featured recursive procedures that operated on list structures.

The logical paradigm was epitomized by uniform proof procedure resolution-based derivation (proof) finders obinson 1965 According to the logical paradigm it was “cheating” to incorporate procedural knowledge reen 1969

Procedural embedding of knowledge

Planner was invented for the purposes of the procedural embedding of knowledge ewitt 1971and was a rejection of the resolution uniform proof procedure paradigm obinson 1965 which
#''Converted everything to clausal form.'' Converting all information to clausal form is problematic because it hides the underlying structure of the information.
#''Then used resolution to attempt to obtain a proof by contradiction by adding the clausal form of the negation of the theorem to be proved.'' Using only resolution as the rule of inference is problematical because it hides the underlying structure of proofs. Also, using proof by contradiction is problematical because the axiomatizations of all practical domains of knowledge are inconsistent in practice.

Planner was a kind of hybrid between the procedural and logical paradigms because it combined programmability with logical reasoning. Planner featured a procedural interpretation of logical sentences where an implication of the form can be procedurally interpreted in the following ways using pattern-directed invocation:
#Forward chaining (antecedently):
#:
#:
#Backward chaining (consequently)
#:
#:

In this respect, the development of Planner was influenced by natural deductive logical systems (especially the one by Frederic Fitch 952.

Micro-planner implementation

A subset called Micro-Planner was implemented by Gerry Sussman, Eugene Charniak and Terry Winograd ussman, Charniak, and Winograd 1971and was used in Winograd's natural-language understanding program SHRDLU, Eugene Charniak's story understanding work, Thorne McCarty's work on legal reasoning, and some other projects. This generated a great deal of excitement in the field of AI. It also generated controversy because it proposed an alternative to the logic approach that had been one of the mainstay paradigms for AI.

At SRI International, Jeff Rulifson, Jan Derksen, and Richard Waldinger developed QA4 which built on the constructs in Planner and introduced a context mechanism to provide modularity for expressions in the database. Earl Sacerdoti and Rene Reboh developed QLISP, an extension of QA4 embedded in INTERLISP, providing Planner-like reasoning embedded in a procedural language and developed in its rich programming environment. QLISP was used by Richard Waldinger and Karl Levitt for program verification, by Earl Sacerdoti for planning and execution monitoring, by Jean-Claude Latombe for computer-aided design, by Richard Fikes for deductive retrieval, and by Steven Coles for an early expert system that guided use of an econometric model.

Computers were expensive. They had only a single slow processor and their memories were very small by comparison with today. So Planner adopted some efficiency expedients including the following:

*Backtracking olomb and Baumert 1965was adopted to economize on the use of time and storage by working on and storing only one possibility at a time in exploring alternatives.
*A unique name assumption was adopted to save space and time by assuming that different names referred to different objects. For example, names like Peking (previous PRC capital name) and Beijing (current PRC capital transliteration) were assumed to refer to different objects.
*A closed-world assumption could be implemented by conditionally testing whether an attempt to prove a goal exhaustively failed. Later this capability was given the misleading name " negation as failure" because for a goal it was possible to say: "if attempting to achieve exhaustively fails then assert ."

The genesis of Prolog

Gerry Sussman, Eugene Charniak, Seymour Papert and Terry Winograd visited the University of Edinburgh in 1971, spreading the news about Micro-Planner and SHRDLU and casting doubt on the resolution uniform proof procedure approach that had been the mainstay of the Edinburgh Logicists. At the University of Edinburgh, Bruce Anderson implemented a subset of Micro-Planner called PICO-PLANNER (Anderson 1972) and Julian Davies (1973) implemented essentially all of Planner.

According to Donald MacKenzie, Pat Hayes recalled the impact of a visit from Papert to Edinburgh, which had become the "heart of artificial intelligence's Logicland," according to Papert's MIT colleague, Carl Hewitt. Papert eloquently voiced his critique of the resolution approach dominant at Edinburgh "…and at least one person upped sticks and left because of Papert." acKenzie 2001 p 82.
The above developments generated tension among the Logicists at Edinburgh. These tensions were exacerbated when the UK Science Research Council commissioned Sir James Lighthill to write a report on the AI research situation in the UK. The resulting report Lighthill 1973; John McCarthy (computer scientist)">McCarthy