2 ;;Quote: 17 man-months to write requirements for a working A-7 flight program with tight memory and time constraints

3 ;;Quote: when writing requirements want to state questions before trying to answer them; otherwise prejudiced towards easily answered questions

4 ;;Quote: in the hardware interface description, every input or output described by a data item form

5 ;;Quote: a data item in a hardware interface description has essential characteristics and arbitrary details; the later may differ over devices

5 ;;Quote: essential information in a specification must not rely on arbitrary details; e.g., use mnemonic names instead of numbers or sequences

5 ;;Quote: in describing a system, used informal templates for value descriptions with blanks for data values; very helpful

5 ;;Quote: describe input and output in terms of external resources and effects

7 ;;Quote: every function can be described by the output data items that it uniquely determines

7 ;;Quote: a demand function includes the events that invoke it; specify maximum delay between request (event) and action

7 ;;Quote: a periodic function needs start and stop events, conditions that effect it, and bounds on its repetition rate

7 ;;Quote: requirements given as functions from aircraft operating conditions to outputs; e.g., ??LATGT70 changes value at 70 latitude

7 ;;Quote: an event occurs when a condition changes between true and false

7 ;;Quote: use text macros for derived quantities; e.g., the !ground track angle! and its definition

8 ;;Quote: '@T(...)' denotes the event of a condition becoming true; can be guarded with a 'when' clause

8 ;;Quote: defined modes for the system; each mode corresponds to a set of true conditions

9 ;;Quote: describe periodic functions with condition tables; behavior depends on time interval, mode and conditions

9 ;;Quote: an event table gives the periodic or demand function to execute when a system mode holds