Statement	References
1.	For analysis, modelling and control of manufacturing systems, one of the tools that is extensively used is Petri Nets (PN). Though PN have proven very useful in analysis and control of manufacturing system, it can be difficult to draw a PN directly from the manufacturing bill of materials (BOM). PN cannot provide a mathematically complete dynamic description of Discrete Event System (DES). The PN marking transition equation provides a partial description, but it is incomplete in that it has not yet been demonstrated how to determined the allowable firing vector. It will shown that the Discrete Event Controller (DEC) equation provide together a complete dynamical description of DES. This allows one to control an actual work cell using the DEC logic, and to simulate on a computer the time behaviour of the controlled system using the DEC equation plus the PN marking transition equation.	Jose Mireles, Jr., On the Development and Implementation of a Matrix-Based Discrete Event Controller, The 9th Mediterranean Conference on Control and Automation, Dubrovik, Croatia, June 2001.
2.	Visual programming differs from textual programming in term of expressing the syntax and semantics of programming languages. Visual programming uses visual syntax which means that some terminals are able to display pictures or forms or other illustrations. A visual syntax may incorporate spatial information and visual attributes such as colour, depth and location. Purely Visual Languages Systems Hybrid text & Visual Programming Systems Other VIPR, Prograph, Pictorial Janus, Labview, Visual Engineering Enviroment (VEE), HI-VISUAL, Vista Visual Basic, Visual Works, Visual J++, Visual C++, OpenStep, ObjectWorld, Rehearsal World Pygmalion, ThingLab, Forms/3, Pursuit, Vampire, ChemTrains, BITPICT, ASP, NoPumpF,NoPumpII, Penguims. Visual programming addresses two important issues in software engineering. Firstly, it enables users to master the complexity of programming by visualizing. The raising of the abstraction to the visual level reveals semantic relationships among programme entities and makes it more understandable. Another one is increasing productivity which gained either through the ease of using the system or the increase in communication among the developers and the users of the systems, because the users can usually understand the beginning process of the designing the systems.	Rodina Ahmad, Visual Languages: A New Way of Programming, Malaysian Journal of Computer Science, Vol. 12 No. 1, pp 76-81, June 1999.
3	Many physical systems are hybrid in these senses that they have barriers or limitations. Inside the limitations they are modelled with differential equations. A natural way to model these systems is to use a mixture of differential equations and inequalities. Other systems have switches and relays that can be naturally modelled as hybrid systems.  These hybrid models appear in many areas. Typical examples are flight control, air traffic control, process control, robotic and etc. An example of this when a nonlinear system is modelled with a set of linear models each one covering a part of the state space.   General Hybrid Control Strategy Therefore, the application of hybrid modelling and control can be an interesting approach to improve plant performance, efficiency, safety and reliability.	A.Gambier, E. Badreddin, “Application of hybrid modelling and control techniques to desolation plants”, Elsevier Science B.V, Desilation 152(2002) pp 175-184,2002.