Definition of PNL
Let’s use the notation PNL for pseudo natural language and PNLU for PNL understanding. The former denotes a class of languages, while the latter denotes a kind of technique for processing PNL. Generally speaking, PNL looks very similar to natural language, but can be understood, analyzed and compiled by computer to an extent by which it can meet the need of some application, for example compiling a text book in a knowledge base for expert consultation.
As an example, the following tiny grammar implies the key structure of a general classification statement:
〈Classification Sentence〉::=[〈Leading word〉<Don’t care>,]〈classification leading sentence〉
〈Leading word〉::=According to | Based on
〈classification leading sentence〉::=〈Don’t care〉〈classification word〉[〈number〉[main]〈type word〉[,〈sequence of Don’t care〉]] | There〈be word〉〈number〉[main]〈type word〉of〈Don’t care〉. They are〈sequence of Don’t care〉.
〈classification word〉::=〈be word〉classified into | 〈mood word〉be classified into
〈be word〉〉::= is | are
〈type word〉::= classes | types | sorts | kinds ……
This grammar may recognize sentences like: Blood cellsare classified into two types,red blood cells, white blood cells.