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In procedural programming languages, the order of executing the statements may follow a regular pattern, including sequences of statements, conditional and branching statements and loops. On the other hand, regular languages can be represented by finite state acceptors (finite automata), by regular expressions and by (a special form of) railroad diagrams (syntax diagrams) allowing alternatives, option, concatenation and iteration. Context-free languages can also be described by (the general form of) railroad diagrams allowing also recursion. Based on the analogy of finite automata and railroad diagrams, the transformation between node-labelled and edge-labelled graphs, special infinite state automata, namely the fractal automata, are established to characterize the class of context-free languages. Deterministic and linear variants are also investigated. To establish these connections, we also define such variants of pushdown automata that accept the deterministic context-free and linear languages by empty stack. A transformation between the pushdown automata and fractal automata is also shown. The proposed model gives some new insights and a new view of context-free languages, deterministic context-free languages, linear context-free and deterministic linear context-free languages.

In Reconfigurable Manufacturing Systems (RMSs), the structure of the system can be changed during execution of the system. This reconfiguration can be motivated by a new requirement in the production process, or to avoid some problems caused by machines breakdowns. These systems offer a high flexibility leading to more productivity and efficiency. However, their design is more complicated implying new techniques and paradigms. The use of formal high level Petri Nets offers the ability to design these systems and to analyse or prove their properties. In this paper, we apply Reconfigurable Object Nets (RONs) for the modelling, simulation and analysis of reconfigurable manufacturing systems. We propose a formal approach, where the reconfiguration is specified as graph transformations, the simulation is realized using the RON-tool, and the analysis exploits some software tools such as TINA-tool and PIPE-tool.