A Sufficient Condition for Erasing Productions to Be Avoidable
In each grammar model, it is an important question whether erasing productions are necessary to generate all languages. Using the concept of grammars with control languages by Salomaa, which offers a uniform treatment of a variety of grammar models, we present a condition on the class of control languages that guarantees that erasing productions are avoidable in the resulting grammar model. On the one hand, this generalizes the previous result that in Petri net controlled grammars, erasing productions can be eliminated. On the other hand, it allows us to infer that the same is true for vector grammars.
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