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. 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 which featured recursive procedures that operated on list structures.

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

Procedural embedding of knowledge

Planner was invented for the purposes of the procedural embedding of knowledge and was a rejection of the resolution uniform proof procedure paradigm, 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.