System structuring model

Giving reasons for your answer, suggest an appropriate system structuring model for the following systems: (15 points) (a) a computer network system to use OSI reference model of network protocols (b) a computer-controlled video conferencing system which allows video, audio and computer data to be visible to several participants at the same time (c) an automated ticket issuing system used by passengers at a railway station
Giving reasons for your answer, suggest an appropriate control model for the following systems: (10 points) (a) a word-processing system (b) a real-time system to control safety systems in a chemical factory
The concepts of coupling and cohesion provide a valuable framework for thinking about software modularity. What are the meaning of coupling and cohesion ? Which coupling and cohesion are the most desirable ? Explain why maximiz-ing cohesion and minimizing coupling leads to more maintainable systems. (15 points)