On this page I put scans of papers that I could not find online, and that have appeared many years ago.
The family S(LIN,REG) of languages obtained by (noniterated) splicing linear languages using regular rules does not coincide with one of the Chomsky families. We give a characterization of this family, and show that we can replace the regular rule set by a finite one.
A "trip" is a triple (g; u; v) where g is, in general, a graph and u and v are nodes of that graph. The trip is from u to v on the graph g. For the special case that g is a tree (or even a string) we investigate ways of specifying and implementing sets of trips. The main result is that a regular set of trips, specified as a regular tree language, can be implemented by a tree-walking automaton that uses marbles and one pebble.
An elementary net system is the basic model of net theory. The state space of an elementary net system is formalized through the notion of the case graph, which is an edge-labelled graph with a distinguished initial node. The paper investigates syntactic, i.e., graph theoretic properties of case graphs of elementary net systems. In particular it studies the structure of isomorpisms between case graphs.