## GLOSSARY FOR PARSING TERMS 

  - pattern
      A very general term which is at the heart of how human beings
      understand the world. Formal languages specify patterns in
      one-dimensional alphabets of symbols; they determine if a 
      particular sequence of symbols is included in a given language
      or not.
  - formal language
      A set of sequences of symbols (letters) arranged in a single
      line. For example (aa, ab, ba) is a language with symbols
      "a" and "b". 
  - markdown
      a minimalistic way to specify the structure/appearance of 
      a plain-text document.
  - virtual machine
      a logic machine which is implemented in software but not in 
      hardware (silicon logic circuits).
  - lex/parse
      2 phases often used during compilation/transformation/translation
  - recogniser
      A piece of software that determines whether a given input has 
      a correct format for a given language or data format. The 
      recogniser does not transform the input in any way, it simply
      returns true or false.
  - bnf, backus-naur form 
      A way to specify the structure of a context-free language. This
      is called the "grammar" of the language. 
  - context-free language
      A simple type of (formal/mathematical) language which has often
      formed the basis for computer languages. A context-free language
      is more complex than a "regular" language but (much) simpler 
      than human language
  - regular language
      A very simple type of (formal) language which is familiar to 
      programmers from "regular expression" patterns. In general, a 
      regular language cannot express "nested" structures (that is:
      text which is contained by other text delimiters). These are the 
      patterns that sed and grep and see.
   - natural language, human language
      These languages involve grammars in which there is an interdependence
      between semantics and grammatical structure. For this reason 
      no good algorithms have yet been developed for the translation
      of human language (despite corporate hype and publicity).