91Ó°ÊÓ

Explain why it may be necessary to design the system architecture before the specifications are written.

Explain why design conflicts might arise when designing an architecture where availability and security requirements are the most important functional requirements.

Giving reasons for your answer, suggest an appropriate structural model for the following systems: An automated ticket-issuing system used by passengers at a railway station A computer-controlled video conferencing system that allows video, audio and computer data to be visible to several participants at the same time A robot floor-cleaner that is intended to clean relatively clear spaces such as corridors. The cleaner must be able to sense walls and other obstructions.

Real-time systems usually use event-driven models of control. Under what circumstances would you recommend the use of a call-return control model for a real-time system?

Giving reasons for your answer, suggest an appropriate control model for the following systems: A batch processing system that takes information about hours worked and pay rates and prints salary slips and bank credit transfer information A set of software tools that are produced by different vendors, but which must work together A television controller that responds to signals from a remote control unit.

Discuss their advantages and disadvantages as far as distributability is concerned of the data-flow model and the object model. Assume that both single machine and distributed versions of an application are required.

Should there be a separate profession of 'software architect' whose role is to work independently with a customer to design a software system architecture? This system would then be implemented by some software company. What might be the difficulties of establishing such a profession?