EOL systems with control devices

SummaryThis paper is concerned with extended OL systems and the effects (with respect to the generative capacity) on these systems caused by1)regular control on the use of subsets of productions2)appearance checking3)minimal table interpretationand their combinations. Among other things it is proven that the effect of 3) is strictly stronger than the effect of both 1) and 2), and equal to the effect of the combination of 1) and 2). This implies among other things that the effect of appearance checking on the systems with regular control is significant.Finally the notions of matrix and vector control are introduced, and the effects of these mechanisms are investigated. This leads to results very much different from corresponding well-known results for context-free grammars.