To obtain a Chomsky normal form grammar we need to eliminate all of the productions of . Each string of symbols along the way is called a sentential form. languages; rewriting any number of symbols in a sentential form is equivalent It follows from Penttonen Normal Form for context-sensitive grammars [ 19] that. Sentential Forms. A sentential form is the start symbol S of a grammar or any string in (V union T)* that can be derived from S. Consider the. SF-languages, i.e., languages which equal the set of sentential forms of a context -free grammar, possess some of the properties of context-free. A sentential form is any string derivable from the start symbol. Thus, in the derivation of a + a * a, E + T * F and E + F * a and F + a * a are all sentential forms as. Context Free Languages and Grammars The above generates the language 0 ∗1(0 + 1)∗ replaces the leftmost non-terminal in the sentential form. In Right. All the sentential forms containing no non-terminal symbols which can be produced from S Languages in this class are often given the name context sensitive. and if S ⇒ rm α we say that α is a right-sentential form. Note: L(G) is those sentential forms that are in T. ∗ language should be unambiguous. • Unfortunately. SF-languages, i.e., languages which equal the set of sentential forms of a context -free grammar, possess some of the properties of context-free languages but.