Terminal Symbol Set

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A Terminal Symbol Set is a Formal Alphabet (composed of Terminal Symbol) that is associated to a Formal Grammar.


  • http://www.csee.umbc.edu/help/theory/lang_def.shtml
    • Alphabet
      • A finite set of symbols.
      • An alphabet is often denoted by sigma, yet can be given any name.
      • B = {0, 1} Says B is an alphabet of two symbols, 0 and 1.
      • C = {a, b, c} Says C is an alphabet of three symbols, a, b and c.
      • Sometimes space and comma are in an alphabet while other times they are meta symbols used for descriptions.


  • (Kakkonen, 2007) ⇒ Tuomo Kakkonen. (2007). “Framework and Resources for Natural Language Evaluation." Academic Dissertation. University of Joensuu.
    • Definition 3-1. Symbol, terminal and alphabet.
      • A symbol is a distinguishable character, such as “a”, “b” or “c”.
      • Any permissible sequence of symbols is called a terminal (also referred to as a word).
      • A finite, nonempty set ∑ of terminals is called an alphabet.
    • Definition 3-2. String and sets of strings.
      • Let Σ be an alphabet.
      • A finite sequence of symbols S=(x1 x2… xn), n≥0, x∈Σ is called a string in alphabet Σ.
      • The length |S| of string S is n.
      • The empty string is the sequence of length 0; written ε.
      • Σ* is the set of all strings in Σ.
      • In addition, Σ+ = Σ*- {ε}.
    • Definition 3-3. Language and sentence.
      • Let Σ be an alphabet.
      • Any subset [math]L[/math] of Σ* is called a language over alphabet Σ.
      • Sequence δ = (α1 α2 … αn), where αiLi, 1≤in, n' ∈ natural numbers, is called a sentence in language L.