Tinkertoy Tower Design Post Mortem Discussion
The point of the exercise • “It is your job to discover the system requirements.” • Who is the customer? • Exercise consists of 2 phases: • Design (40 minutes) • Implementation (15 minutes)
Design phase • Planning (problem & solution) • Classes of components • Deliverables are a design and its inventory of technologies • Finding & fixing issues cheap • Deadline (40 min) • Penalty (large) • Bonus (smaller) • Ends with PDR
Implementation phase • Build • Specific components (objects) • Deliverable is a prototype • Must pass system test • Resolve unplanned issues • but at a steep cost • Deadline (15 min) • Penalty (absolute) • Bonus (large) • Ends with CDR
Operations phase • Not addressed in exercise • Customer will operate • Design must address maintenance and other life cycle issues • Never ends • The clearer the milestones between phases, the better
Prototypes must pass tests • Include cost of test equip. • Environment is described • Flat hard surface • Free standing • Minimum test is stated, but • Additional requirements are always present
Design life • Implicit in every project • Should be explicitly stated • Y2K was a design life issue • Observatory systems can have an especially long life • STB running since 20 July 1993 • Lifecycle planning • Retirement requirements • Evolving environments
Analyze Risks • Unprecedented challenges • Software projects are notorious for collapsing under own weight • Either a project is tied to core mission of the organization or • It isn’t - which is riskier?
Implementation Issues • Different technologies have different acquisition costs • Different recurring costs • Integration issues • Quality assurance • Maintenance and reliability • Availability of HW/SW/personnel
All design is evolutionary • Improve Tinkertoy exercise? • Display example tower? • “Here is a 60’ tower. It earns minus $33K. Why?” • Swap designs w/ other teams? • Hand out requirements with less prodding from teams? • One shared can of Tinkertoys during design phase?
Not applicable to software? • The tower exercise is only a cartoon model of real towers • No civil engineering, per se • No beams or trusses • No welds or rivets • No tension or compression
The essence of Systems • System engineering is responsible for identifying and satisfying the life cycle requirements. • One problem • Many solutions