2.5 An overall architectural description should be produced to identify sub-systems
making up the system. Once these have been identified, they may be specified in
parallel with other systems and the interfaces between sub-systems defined.

2.6 Exercise for the Student.

2.7 The key features of the solution are:
• Database with different types of data
• Video control system
• Operator console system
• River data collection
• Weather system links
• Communication control system
See Figure 2.1.

 

2.9 Arguments in favor of Systems Engineering as a discipline include, 1) it is an interdisciplinary profession consisting of specifying, designing, implementing, validating and maintaining the system as a whole. System engineers are concered with S/W and H/W and the system interactions with users and it's environment. Difficult to find a single system engineer that has the knowledge to satisfy the interdisciplinary requirements for the job.

3.1 (a) Anti-lock braking system Safety-critical system so method based on formal
transformations with proofs of equivalence between each stage.
(b) Virtual reality system System whose requirements cannot be predicted in advance
so exploratory programming model is appropriate.
(c) University accounting system System whose requirements should be stable
because of existing system therefore waterfall model is appropriate.
(d) Interactive timetable System with a complex user interface but which must be
stable and reliable. Should be based on throw-away prototyping to find requirements
then either incremental development or waterfall model.

3.2 Programs developed using evolutionary development are difficult to maintain because

3.3 The waterfall model is accommodated where there is a low specification risk and no
need for prototyping etc. for risk resolution. The activities in the 2nd quadrant of the
spiral model are skipped. The prototyping model is accommodated when the
specification phase is limited and the prototyping (risk resolution) phase
predominates. The activities in the 3rd quadrant of the spiral model are skipped or
reduced in scope.

3.4 User requirements are abstract statements of the system requirements for the customer and end-user of the system; system requirements are a more detailed description of the functionality to be provided.

3.6 Components of a design method are:
A defined set of system models
Rules that apply to these models
Guidelines for design 'good practice'
A model of the design process
Formats for reports on the design