software

Zero one infinity rule

• Rule of thumb proposed by Willem van der Poel
• Argues that arbitrary limits on instances of data or structure should not be allowed
• We should only allow
  • 0
  • 1
  • Infinity
• Software should not put arbitrary limits on an entity

Example

Using file systems, how does this apply?

• 0
  • Topmost directory has zero parent directories
• 1
  • Each subdirectory has exactly one parent
• Infinity
  • Each directory can contain ~infinite files or subdirectories
  • Limitations may be defined by things like storage space but not by software