Based on fundamental principle of computational terminology, the phrase-terms are syntactically parsed by the phrase structure grammar (PSG).

The current syntax tagging models are customarily based on PSG (Phrase Structure Grammar) or DG (Dependency Grammar), but all have some shortcomings.

To implementation of efficient parsing of grammars, a new class of phrase structure grammars called overlap-free grammar(OFG) with heavily restricted rewriting rules is defined.